Ok so this may have already been posted but I'm gonna ask I have a 2000 blazer 4x4 with 4.3 vortec motor had to change motor due to it being blown. The new motor came out of a 99 s-10 and had a miss fire on number 4 and 6 and was only hold 90 lbs of compression so ran 2 cans of seafoam through it now number 4 doesn't have miss fire and compression is holding at 120 number 6 is still miss firing and only holding 90 lbs compression ran another can and half through it can still feel miss in it. Should I run more seafoam and change plugs cause when I put seafoam in it it smoke like crazy...