Problem:
My S1.5 R33 used to missfire from around 4500rpm til about 5500rpm @ 12psi+ (especially in the cold). I tried everything, from installing an SAFC II piggyback to tune the AFR to regapping my spark plugs etc.
Solution:
The stock coil packs have a hairline split on the side of them, which at high boost levels, the spark tends to not follow through to the spark plug, but jumps out of the coil pack. After sealing up all my coil packs, my car runs much smoother now, I can boost it to 16psi and I dont get any missfiring.
D.I.Y. Fix:
For a quick and cheap fix for this problem.. (the following was done with spark plugs regapped to 0.8)
R33 GTS-t Fix (Im guessing that the same problem occurs on the R32 & 34):
1. Take off the plastic cover in the middle of the engine (between the tapper covers) which covers your coil packs
2. Unplug and unscrew each coil pack (all six) and take them out
3. Holding the coil packs vertically, inspect the sides and locate the hairline split (as shown below)
4. Once you locate the split, using GOOD electrical tape (cheap stuff WONT work), tape over the split a couple of times, making sure the tape sits flat over the split and seals it firmly (as shown below)
5. Once you have taped up all 6 coil packs, screw them back in place and reconnect the plugs
6. Place your plastic cover back over the coil packs (I have left mine off for better cooling of the coil packs)
Done!
MORE HELP:
For more info on taking out the coil packs ---> http://www.skylinesaustralia.com/forums/in...showtopic=42819
Another alternative is buying Splitfires, but this is around $700+ dearer to do..
PS. Make sure you use GOOD electrical tape, as cheap stuff tends to get hard and peel off from the heat.
EDIT: Or as QRI05E recommended - for a more reliable seal, use 'Shelleys Industrial Silicon Sealer 401' for only $11 @ Bunnings.