I made an appointment at SLP on March 25th to get the pulley swap and a 180 thermostat installed. Now SLP told me that they use the 3.5 pulley instead of the 3.4, what I want to know is is it ok to install the 3.5 on my 02 BonnevilleSSEI. Most of the threads that I read on this forum, everybody seems to have the 3.4 pulley. For the time being I only plan on doing the pulleyswap,thermostat,and the cai mod(still waiting on the
ADTR CAI).

The only thing that would sway your decision to one pulley diameter or another is the amount of boost and performance you want. 3.5 is less extreme than 3.4, so go for it. No big deal, and probably not a noticeable difference between the 2. 3.6, 3.4, and 3.25 just happen to be the common sizes chosen, as they're the sizes manufactured by our esteemed vendor, Pulley Boys. You'll end up right between the first 2 performance diameters he manufactures.

SLP sells the 3.5 vs the 3.4 because that is the option they have for the supercharged GTX, you will not notice hardly any difference between the two, but the 3.5 will work well on an otherwise stock car. I would advise you to ditch the airbox and put a K&N cone filter on when you do the pulley, also changing the plugs to AC 41-932 plugs gapped at .058 which are one heat range colder than stock will keep you from having to worry about KR.