I have a 93 Z28. I installed a MSD opti, BBK ceramic coated headers, K&N cold air, JET stage II chip and a 160 deg thermostat. I installed all of this at the same time. Now it runs great when I start it up cold, but when it is warmed up it sputters between 1000 & 2500 rpm, but only when in gear. Above 2500 it runs great. In park or neutral it runs fine through the entire RPM range. The SES light is NOT on, so im guessing I have no codes. I removed the chip thinking that might be the cause, nothing changed. Any ideas? Anything will help...