i have a 1990 rx7 convetable the car will not idle below 1500 rpms and after about 15 min of driving i get a check engine light and it will bog down at 3500rpm but if you are light on the throttle it has no problem going past that if you have and info that would be great

 

Check for vacuum leaks.

Make sure the cold start cam and thermowax are not sticking.

Search "3800 RPM hesitation" for help on the 3500 RPM issue.