Glad the plugs and coils helped. It may not be because the coils are aftermarket, but just because they're new. Having proper ignition will improve everything about the engine's running and restore the boost and airflow, which is why you're now hearing the full effect of the turbo and exhaust. Having airflow mods won't cause you to run lean - MAF, O2s, and MAP sensor (if your car is an 01+) monitor the airflow and allow the ECU to compensate for the higher flow. For the plugs, try Advance Auto - my local store had them in stock last I checked.

 

I tried all of those places. Finally on my last auto parts store attempt. O'Reilly auto had it and they had one pack left. Go figure. It's funny, when I originally upgraded my ECU, I got new plugs, coils and had the new HFC installed and I didn't really notice a difference.

Makes sense about the compensation about the airflow. Didn't think about that. Time to get a new O2.

Appreciate the knowledge.