now i know my 96 ssei has the stock 3.8 inch pulley, my question is, how can i determine what size my car can handle... i see that alot of the cars on this site have 3.4 inch pulleys, but what other mods should i worry about making first? i already have a cai and 2.5" cat back
All motors react alittle bit different but get some plugs that are one heat range colder (or stock plugs might be ok if it is not warm where you are. Untill it warms up) & a 180 degree thermostat and you should be good for a 3.5" or 3.4" pulley. You shouldn't run any gas lower then 92 octane also.
But the only safe way of knowing how much boost u can run is to scan and do all you can do to keep KR down.
Get a scantool first. You MUST know if you get KR with a smaller pulley. You've done some good basics already. I'd GUESS you'd be safe with a 3.5", and possibly a 3.4" depending on how your car reacts to it. All are different.