How fast or slow GBR Winny is in reality isn't the issue. The statement about people tuning rental cars with some sort of glitch is the elephant in the room as far as I am concerned.
The below statement was in reply to GBR Winny's post in the ForzaRC section of the forums.
Originally Posted by: RPM Swerve 
I'm surprised it took this long for this to reach the forums. Makes you question the pre-top 24 rounds, though I'm not sure who actually exploited this.
For those reading this thread, this glitch only impacted cars that can be tuned in stock form which were usually race cars.
Swerve posts on these forums regularly and is lighting quick. Not that being fast matters, but this post by RPM Swerve is pretty much a smoking gun. This is the first I have heard of such a glitch of people tuning rental cars. If this was happening during the ForzaRC it basically makes the ForzaRC a joke. If people are doing this in the Rivals ie Bounty Challenges, Qualifiers, etc. those are also compromised.