I recently had a coilpack die on me and as I had two others that were original to the car, I decided on replacing all three.
After this I found the car started to stutter when it's been ragged for a while. Every so often it also wouldn't let me rev past 3000rpm, which I guess is it going into limp mode.
After trying a few different things (throttle body clean, check for air leaks etc), I replaced the N75J valve with the original and it seems to have cured the issue. I've been running the J valve for a while now with no issues, so it seems strange that a coilpack change should cause these problems. With the original valve back on, my car doesn't feel nearly so reponsive
Before I stick this J valve in the classifieds, is there anything else I should look at? I running Bosch Super4 plugs, should I try changing these to something else, would it make a difference?