I don't understand...are you leaving black tire marks from corner to corner? Are you lifting the front wheels off the ground when you step on the gas and it won't allow you to turn, causing an unsafe condition?

Are your rear tires worn out after 1K kms?

Even if the the answers to the above questions are all "yes"...I really still don't understand...but then I'm having a tough time focusing on things other than how I'm gonna put this M5 V10 motor in this MCoupe's engine bay....

just kidding...and go for the more powerful motor, you can always step on the gas pedal less...

Be good,
TomK