I currently own a 2008 GS and also just purchased a 2015 RT-S.
In 2009 an engineer from the one of the Aprilla race support teams developed a kit that put the Can Am 990 back close to the original specs of the 990 before Can Am de-tuned it for liability issues.
The kit included a set of high compression pistons, 02 modifier, new intake, exhaust. The setup makes 140 hp and halls ars! I have put 11,500 mls on the GS since the update with zero issues. I have raced several 600 crotch rockets and beat them to 100, after that the Spyder is just to heavy to stay with them. I have also raced the AeroCharger turbo Spyder setup at Spyderfest, beat that setup by 10 lengths in about a 1/4 mile, the techs were there from AC, they were not happy... 0-60 in just over 4 seconds
Trike is currently for sale in Minneapolis.
Making the RT go fast is the next project...
Daniel