As title says, Story is my car is at a excellent tuners and has been for a while and they have come across this horrid missfire BUT only when its at 28 psi upwards the car has made good hp which im happy with it but if they wind the boost down to 26 psi the missfire goes?? just to say everything has been changed ie sparkplugs,coil,injectors etc etc, i was thinking maybe an airleak at high boost or would they pick it up via fueling??

 

What are the replacement plugs and what have they been gapped at?

As it's so little difference between it are you sure it's not a boost cut you are experiencing?

Martin

 

It can't be a very good tuners if they with the equipment can't find the problem, they need to be watching the emissions when it misses, could be lots of things even a injector breaking down, ie they can over heat, very rare but when they do they simply keep stuttering, worsens under load.
tabetha

 

Hope u get it sorted mate