McFartenplop

My car has developed an issue in the last week.

Im running Simtek, GT30, rotated set up, 800cc injectors @around 450bhp.

3rd, 4th and 5th have developed a kind of pulsing/misfire issue when on full boost. Its like it misfires then clears then misfires again. On off on off.
Ive changed the coilpacks from the old 95 ones to the newage but symptoms still persist.

I have now noticed the rotated uppipe has split at the flange so this is being fixed as I type.

Could this cause the AFR problems and therefore underfuel when on boost and give the above symptoms or does it sound ignition replated?