Hello and Welcome to the MCF! I agree with John, the hand held tuners are a gimmick, do some research on them and you might agree. I think what John says doing the "Mail Order Tune" is the most cost effective option. You pull your cars computer out, mail it in and the tuner custom tunes it to change the parameters of the computers factory settings. They can delete the factory speed limiter, change tranny line pressure shifting points, etc. And I think some tuners like on the forum here you just give them your Montes VIN number and they can mail you a computer tuned to that VIN, you swap them out and mail your old one to them. It's actually pretty little money in my opinion.
Here is a link to a member who can square you away.
PCM Service ('98-'05 3800/3400/3100)
You don't have a 3" exhaust from front to back do you? Or does it start 3" after the CAT Converter. That's way to much exhaust unless you Turbocharged / or highly Supercharged. So I bet it's only after the converter or just the tips after the mufflers...