94 6.5 blazer...started a couple months ago, erratic, and not a real problem....now it is more frequent....when she misfires a puff of smoke is produced....is it an injector problem....otherwise truck runs good....

The first thing I would do is put a clear plastic hose on the injection pump fuel return to see if you are getting air in the line, does it misfire more when its cold?

I am in the middle of fixing that on my truck I would make sure that the lift pump is working right.

when it first started, it never missed when it was cold, seemed to be more prevelant as she was hot or driving....when it happens the engine goes "PUNK" and a puff of smoke (i guess its un burnt fuel/ shoots out the exhaust....it has really got me spoofed....i tried the fuel line trick,, nothing...not leaking anything either....could a bad injector cause this???

bad fuel? dregs in the fuel filter assembly? have you tried a clean up dose of power service? just throwing out cheap fix ideas.