It runs great, no funky sounds, wouldn't even know it has a problem except for the fact that it won't go over 40ish mph. Also has a problem going uphill. Hooked it up to computer but it isn't pushing any codes. Could it be the map sensor?

 

The first thing I would look into is a plugged up catalytic converter. That would allow it to run normally and not have any power

 

I've had this problem twice. First time was a clogged cat, second time it was a seized caliper.