Hi,

Looking for some info on which type of Spark Plug should I be using in my cossie and what gap they should be.
I have a 1992 sierra 4x4, running 330bhp, stage 3 chip. I only bought it a couple of weeks ago and decided to get a service done. But I think he may have put different plugs in it, not sure. The mechanic doesn't know why it's backfiring, checked all the usual, more of a thumping sound through the exhaust now and then, sometimes loud! So I just want to eliminate the plugs. Any help would be great as it's annoying the hell out of me.