Some information
Your speed sounds about right with a little difference on the good side.
I keep the records and statistics for the Sport Air Racing League in Excel so it is easy for me to single out the 320 powered RVs and average the race speeds. So far 78 such race flights have been made. The class for 320 powered RVs is RV Red. The average speed for all is 167.18 kts or 192.37 mph.
Here are the data:
AirVenture Cup 2008 7/27/08 RV Red RV-4 Murphy, Chris 186.01 214.06
Texoma 100, 2008 4/20/08 RV Red RV-4 Murphy, Chris 183.67 211.40
AirVenture Cup 2007 7/23/07 RV Red RV-4 Murphy, Chris 180.33 207.52
AirVenture Cup 2008 7/27/08 RV Red RV-3 Vasey, Bob 179.96 207.10
TVA II 2009 10/18/09 RV Red RV-4 Benton, Cam 179.23 206.25
AirVenture Cup 2007 7/23/07 RV Red RV-6A Klusmier, Larry 178.90 205.87
Thunderbird 150 10/8/11 RV Red RV-7 Baker, Seth 178.53 205.45
Grace Flight 2008 10/5/08 RV Red RV-4 Murphy, Chris 178.51 205.43
Rocket 100, 2010 11/20/10 RV Red RV-7 Baker, Seth 178.47 205.38
AirVenture Cup 2007 7/23/07 RV Red RV-3 Vasey, Bob 178.15 205.01
Taylor 100 2009 3/16/09 RV Red RV-4 Benton, Cam 178.02 204.86
Rocket 100, 2010 11/20/10 RV Red RV-8 Jones, Bryan 177.27 204.00
AirVenture Cup 2007 7/23/07 RV Red RV-6 Weisgerber, David 177.92 203.91
TVA II 2009 10/18/09 RV Red RV-4 Murphy, Chris 176.54 203.16
Rocket 100, 2011 11/19/11 RV Red RV-7 Baker, Seth 175.78 202.28
Thunderbird Air Race, 2012 10/13/12 RV Red RV-7 Baker, Seth 175.60 202.08
Rocket 100 2008 11/23/08 RV Red RV-4 Murphy, Chris 174.92 201.30
West Texas 100 6/6/10 RV Red RV-4 Benton, Cam 174.17 200.43
Rocket 100, 2007 11/18/07 RV Red RV-4 Benton, Cam 174.12 200.37
Taylor 150 4/11/10 RV Red RV-4 Benton, Cam 174.11 200.36
GNAR III, Ephrata, WA 6/16/12 RV Red RV-4 Ford, George 173.91 200.13
Grace Flight 2010 10/2/10 RV Red RV-4 Benton, Cam 173.76 199.95
Pagosa Springs 2010 9/26/10 RV Red RV-4 Benton, Cam 173.65 199.70
Taylor 150, 2013 4/13/13 RV Red RV-4 Robert Faubion, Robert 173.47 199.62
AirVenture Cup 2010 7/26/10 RV Red RV-4 Murphy, Chris 173.00 199.09
Colorado 150 2009 7/23/09 RV Red RV-4 Murphy, Chris 172.90 198.97
Memphis 100 2008 10/19/08 RV Red RV-4 Murphy, Chris 172.78 198.83
Rocket 100 2009 11/22/09 RV Red RV-7A Reiley, Darrell 172.11 198.06
Cleveland Texas Air Race 10/15/11 RV Red RV-8 Jones, Bryan 171.33 197.16
AirVenture Cup 2010 7/26/10 RV Red RV-3 Vasey, Bob 171.17 196.98
Grace Flight 2010 10/2/10 RV Red RV-7 Baker, Seth 171.00 196.77
Texoma 100, 2011 4/16/11 RV Red RV-4 Murphy, Chris 170.51 196.15
Taylor 100 2007 5/20/07 RV Red RV-4 Benton, Cam 170.43 196.13
Pagosa Springs 2010 9/26/10 RV Red RV-7 Baker, Seth 170.45 196.02
Memphis 100 2008 10/19/08 RV Red RV-4 Smith, Dwight 169.88 195.50
Pagosa Springs 100 2009 9/27/09 RV Red RV-4 Benton, Cam 169.78 195.25
Taylor 100 2007 5/20/07 RV Red RV-8 Jones, Bryan 169.45 195.00
Tennessee Valley Air Race 2010 10/30/10 RV Red RV-4 Archord, Jim 169.17 194.72
Sulphur Springs 130 7/18/10 RV Red RV-4 Benton, Cam 168.84 194.30
West Texas 100 6/6/10 RV Red RV-4 Murphy, Chris 167.83 193.14
Big Muddy, Carbondale, IL 6/4/11 RV Red RV-6 Weisgerber, David 167.82 193.12
Pagosa Springs 2010 9/26/10 RV Red RV-4 Faubion, Robert 167.80 192.97
West Texas 100 6/6/10 RV Red RV-4 Faubion, Robert 167.44 192.69
Thunderbird Air Race, 2012 10/13/12 RV Red RV-6A Ahrens, David 167.42 192.66
BSAR II, Three Forks, MT 7/7/12 RV Red RV-4 Keeler, Art 167.27 192.49
West Texas 100, 2007 10/7/07 RV Red RV-4 Benton, Cam 166.40 191.50
West Texas 100 2009 4/12/09 RV Red RV-4 Benton, Cam 166.29 191.36
AirCap 200 8/24/08 RV Red RV-6 Smith, Jim 166.21 191.27
Taylor 150 4/11/10 RV Red RV-7A Reiley, Darrell 165.94 190.96
BCAF 2013 5/3/13 RV Red RV-9 Johnson, Steve 165.76 190.76
Colorado 150, 2008 6/29/08 RV Red RV-4 Murphy, Chris 165.65 190.62
Cleveland Texas Air Race 10/15/11 RV Red RV-6 Behrends, Steve 164.72 189.55
Tennessee Valley Air Race IV 10/29/11 RV Red RV-4 Murphy, Chris 163.35 187.98
Texoma 100, 2011 4/16/11 RV Red RV-6 Smith, Jim 163.38 187.94
Taylor 100 2007 5/20/07 RV Red RV-3 Hackett, Willy 162.96 187.53
Denton 100 2008 6/15/08 RV Red RV-4 Bruggers, Ken 162.71 187.24
TVA II 2009 10/18/09 RV Red RV-6A Phillips, Mark 162.66 187.19
Taylor 150 4/11/10 RV Red RV-4 Faubion, Robert 162.24 186.71
Texoma 100, 2008 4/20/08 RV Red RV-6A Heathco, Charlie 161.75 186.17
West Texas 100 6/6/10 RV Red RV-7 Baker, Seth 161.58 185.94
Great Canadian Air Rally 2010 8/22/10 RV Red RV-9A Wilkinson, Greg 160.53 184.73
Ozark Grove AR, Grove, OK 11/3/12 RV Red RV-6A Heathco, Charlie 160.07 184.21
Northwoods 100 10/8/11 RV Red RV-9 Phillips, Tony 159.97 184.09
Cleveland Texas Air Race 10/15/11 RV Red RV-6 Bivens, Darrell 159.35 183.38
Memphis 100, 2007 10/28/07 RV Red RV-4 Smith, Dwight 158.39 182.28
Great Canadian Air Rally 2010 8/22/10 RV Red RV-9A Murray, Charlie 158.29 182.15
Texoma 100, 2013 4/6/13 RV Red RV-6 Smith, Jim 155.81 179.3
AirVenture Cup (TH) 2011 7/25/11 RV Red RV-4 Crawford, Tony 155.55 179.00
AirVenture Cup 2009 7/27/09 RV Red RV-3 Vasey, Bob 155.54 178.99
Top of the Chesapeake 7/11/10 RV Red RV-4 Winkelman, Steve 155.39 178.83
Lone Star Air Rally 5/14/11 RV Red RV-6A Bivens, Darrell 154.86 178.21
Hill Country 150, 2012 4/21/12 RV Red RV-9A Johnson, Steve 154.33 177.60
Pappy Boyington Memorial Cup 8/18/12 RV Red RV-6 Inkster, Ralph 153.42 176.56
Great NW Air Race 6/13/10 RV Red RV-6A Hungelmann, Bill 152.37 175.35
Texoma 100, 2013 4/6/13 RV Red RV-6A Heathco, Charlie 145.01 166.88
Lone Star Air Rally 5/14/11 RV Red RV-6A McGinnis, Patrick 144.92 166.77
AirVenture Cup 2009 7/27/09 RV Red RV-6 Campbell Steve & John Popel 138.33 159.19
Texoma 100 4/25/10 RV Red RV-4 Benton, Cam 132.78 152.70
Average: 167.18kts 192.37mph