Ok here's the deal a few weeks ago i did the pi swap and put some Hitech stage II's in as well. She runs great from 2,000 rpm's and up but below that it shudders and hesitates like no other. And she won't idle when it gets warm but will when its cold? I've replaced the IAC valve checked for vaccum leaks and don't know what wrong? Could it be running to lean? Could it be that i just need to take it to the dyno? Any suggestions would be great cause i'm at a lose on what it could be??? Thanks