The 103 plugs are too cold for your mods. I highly doubt you will be able to properly run a 3.4 pulley again with your other mods.
And I agree with GeddyLee about the catback. The GT he mentioned was the worst. And let no one kid you, other than at idle, no matter the mods, NO V6 sounds good with loud exhaust. It may sound ok on the inside of the car, but on the outside...crap. Now if you are used to being around 4 cyl's then it isn't quite as bad but on a sliding scale we have good to bad
V8.................V6 cammed..V6..4cyl![]()