I finally got the ASP under drive pulley (25%) and put it on and within 10 minutes the check engine light came on. I scanned it and it said there was a random misfire within the first 1000 rpms of running. I sure didn't feel any though. I cleared the code and later that day it came on again with the same problem, random misfire and one possibility is low voltage on start up. The engine spins over fine though. I removed the pulley and inspected it and it looks perfect so I put the old back on and no more codes. I also tested the battery and alternator and both are fine. Has anyone else had this problem with an UDP? Would an overdrive alt pulley cure it? I don't want to have to return the udp but I sure can't have the light on all the time.