It's not n.a it's the 2.0 turbo model. And the turbo is actually boosting while it's backfiring if that's any help to diagnose the problem

Thanks for the info guys. It has individual coil packs and has had new plugs yesterday. Will check the compression as soon as I can. I was thinking that the timing might have slipped a tooth on the belt leaving a valve open when it shouldn't be. And it's an s reg which is late 98 to early 99. I don'...

I've got a 1998 c70. I replaced the etm that was running low power and limited revs (limp mode?) With a reconditioned one. Since the swap it has got the power back and will rev as normal, but had developed a miss fire back through the inlet manifold. It gives me a p1238 code which I've worked out as...