Today I changed the air filter and installed a Z tube on my 03 6mt sedan. I love the new sound and personality of my car but...... just after the install I noticed my idle was now a about 850 RPM. It has always been at 650 RPM since day one. Also, on my way home, about 39 miles into my commute the Check engine light comes on. The car is running great. So, I check thoe boards, and do the easy ecu reset. This clears the CEL and so far in about 20 miles of driving it has not come back. However, it still idles anywhare from 800 - 850 RPM. Anyone have any ideas on why this is the case?

MAF sensor might've caused the check engine light. Resetting it always helps to make sure its nothing else, so if so far so good, I wouldn't worry bud.

Make sure the MAF is correctly plugged in. Do an ECU reset and drive the hell out of it. She will settle down after you show her who is boss.

Thanks guys, shes driving great, just hope the idle goes back down.

Hey G35John, I had the same problem as you when I installed my Z-tube. It was idling around 850 too, however, when I had my coupe midpipe put on, it went back down to around 650 (and it's still there). No worries bud! And as Cato said, "Keep driving the hell out of it!"

Bad news. I started the car for the first time today and the CEL isntantly came on. I restet the ECU again and it stayed off. Im expecting it to come on in the moring. Im thinking ill just have to take it in to the dealer for it to me looked at and see what code is being thrown.