Hi I have recently had Z22SE replacement engine fitted into my astra coupe. Ever since I have had idle problems, tick over is very lumpy, whilst driving at slow speed it is juddering, once you approach 30-40 mph the car runs fine. I was told to block the EGR valve off, which I have done so. I have today took the car for a 40 mile run, and tick over is exactly the same. When I looked under the bonnet the down pipe leading towards the cat is glowing red, could this be a blockage somewhere, and would this be causing the idle problems? Please Please help me this car has cost me a fortune, and I just want it sorted asap. Cheers