Over the weekend I installed INTENSE-racings level 1 performance package on my 2000 SSEi. After I finished up I took it on it'* first test drive. I noticed that it was running kinda crappy. So, I called my mechanic buddy and he said that it usually takes a couple of days for the new PCM to adjust to all the changes that have been made. Has anyone else experienced this? If so, how long did it take for your car to start running good again. Also, is it always necisary to do the crankshaft positioning learn procedure or do I not need to do it if the car ends up running fine after a couple of days?

If you installed a PCM as part of the package, then yes, you definitely need a CASE learn procedure. Go to the dealer and ask for a Crankshaft Variation Learn procedure, or a Crank Angle Sensor learn procedure, and they should give you what you need. After that, report back here for troubleshooting.

A friendly reminder for them not to re-flash your new PCM wouldn't hurt either

You might also be picking up some knock retard because of the smaller pulley, especially if you havent done any exhaust modifications, more specifically at least a high-flow cat.

You should get ahold of a scantool to see how much KR you are getting, the hot temps outside make it even worse.

In reference to the above comments, you should know that just because a vendor offers a performance package doesn't necessarily mean the parts should go on your car at once. Intense and ZZP do a pretty good job letting you know what you'll need to install a certain mod, but sometimes there are other actions that should be taken prior to parts installation. For instance, you should scan to see if your computer is pulling timing due to knock, or to see how your fuel flow is keeping up with new modifications. Many people come into the game thinking they can just throw parts at a car, and to some extent you can, but sometimes it leads to a performance reduction instead of the intended increase. You really have to "do your homework" and use a scantool if you want to have a firm grasp on the status of your car and the effects of any mods.