Misfires after aftermarket crank pulley install......

[Grand Prix GTP]

I bought an aftermarket off ebay a while back for the Maxima. I recently got it installed and the car runs like crap. The instructions that came with it say it will take 5-7 days for the computer to recalibrate. It's been about 6 now and the car drives worse then when I first got it back. I had a trusted mechanic put it on and he agreed that it would get better within a few days. The engine from what it seems like, misfires around 3k RPMs. Basically the engine sputters... Does anyone know of anything that he might have messed up or not connected some connection that would be doing this? This weekend, if it keeps doing it, I guess will put the stock one back on but don't really want to. Any suggestions??? Thanks

Ohh also, he installed a short throw shifter, but idk how that could effect it. Just trying to think of everything that happened prior to it running well

[Fezzik]

ok bud. need a little more info. What year maxima. If you have a 2001 maxima or earlier does it have the timing ring on the crank pulley. If its a 2k2 or above it does not need the crank pulley.