[fast924S]

Ok thats not good. High boost+ High load + lean mixture = Very high combustion temps and hot spots. Again not good. Do you have a EGT gauge?? if not when you rebuild the engine I would install one, just to keep a eye on whats going on. As for whats wrong. If you can go and buy the gauge set to do a leak down test on the #3 cyclinder. When you do this and if you hear air or feel air comming from the exhaust then there is a bad exhaust valve. IF you hear or feel it comming from the intake then you have a bad intake valve. If you remove your oil cap and feel and hear it from there then you have a bigger problem, eather a hole in the piston or bad rings. If you take the cap off the radiator and its comming from there then you have a head gasket problem. As for how much it will cost it all depends on whats wrong, but I bet for just bearings,rings and some machining and new valves, ect... full stock engine rebuild I would think like $1200-$2000 if you do the all the work.