100% the JAM FCC is wired in correctly according to this guide: http://www.toyotagtturbo.com/showthread.php?t=11807 Earthed properly, connected to a ignition live, and have the wires the right way round. Its nothing the dyno bloke did, as it was like it before. Could it be another shitted up JAM FCC like Al's? I think he was having the exact same problem! Your explanation makes sense, as the boost gauge in dash would jump to full + straight away, and then it just splutters/rpm drops & rises randomly and generally runs like shit. Cheers for the quick reply Rick! I think tomorrow I'm j