I just finished my 3.4" set up and it's a completely different car. The gain in power and change in feel is night and day. I know everyone says look up the properly modding your 3800 car forum but it's a good idea. It's pretty much listed in order what you should do. I did my CAI --> Headers --> PCM --> Plugs&Stat --> 3.4" MPS. The big gains come late when you install the PCM and pulley.