So I just got a SLP lid and put it on and it seemed to go on fine although the fit is a little tight. Anyway when I started the car up the idle is very low around 300 - 400 rpm and acts as if its going to die. So I then take it out on the road it it drives great, power is normal if not better but when I come to a stop the idle drops way down low below 650 -700 rpm which is about normal and then comes back up. The only two things that I obviously had to take off with were the MAF and air temp sensor but I was very careful when removing them from the old lid to the new one. I also disconeted the battery before doing anything. Any ideas on what is causing this surging idle?

 

Disconnecting the battery resets the PCM, it'll take a while for it to relearn the fuel and timing curves. Give it a few starts/cycles and you should be OK.