I have a stock 2006 grand prix supercharged engine. it's a canadian car so the speedo read's in kilometers, anyway i was on the highway and opened her up and the most it wold do is 180 to 185. shouldn't go to the 220 mark or does it sound like something is wrong. The only thing i have on the car is 18" wheels and a cold air intake and it has new plugs and wires.