ok i have been suffering from a missfire for the last month and after changing my plugs and reconditioning my coils, checking for leaks etc etc i had about given up. but today i decided to fit a big blow of valve to my car that i had sitting around for a while so i welded the collor onto my intake pipe put it on connected the vacume off left my standard recirc valve in place but with a blocked off vacume going too it, went up the road voooooom tish..... sounded great, gave it some heavy right foot took it all the way round to the redline...... no missfire???? strange i thought, did it again in the next gear whilst watching my boost gauge, needle went to the marker between 0 and +7 again no missfire so i stopped got out, disconnected my dump valve and reconnected my standard re circ valve, went for a drive up the road again, boosted to nearly +7 on the gauge, felt loads quicker but missfired like crazy after 5000rpm. so whats the problem? my car seems slower to drive now with the new d/v and smoother, but with the standard d/v connected its like an animal with high boost but got that missfire at around 5k+??