Hi all, need some opinions. New to forum but have read threads for years and this one has me wondering. So some back ground info. My son has a 96 blazer 4x4 4.3l W vin. got it about 2 years ago ran good no issues 6 months ago he blew top radiator hose and over heated. Replaced hose ran a little warmer but no other problems. Now the new problem, water pump went out and over heated again this time quit running. After inspecting found leaking intake and blown head gasket on left bank also had some old oil leaks on oil pan so decided to replace all gaskets. Removed motor and tore down cleaned and checked everything used a true straight edge to check block and heads no sign of warpage replaced all gaskets and reinstalled fired it up and ran real rough at idle got a p0300 code and flashing ses. tested map, maf, iac, and fuel system all checked good so checked compression and have 170 psi on left bank all cyl. right bank 45 ,50, 45 did wet test and no change. So pulled it apart and checked torque 3 bolts were about a quarter turn off retorqued and compression came up to 60 psi on all cyl. so my question is could it be a bad gasket or am I missing something? I've been turning wrenches over 30 years and haven't seen this before. Any ideas