Rough Idle and Shaking on Acceleration

['87 Static Slam]

ok guys, im gonna lay out what happened and i would love to have your thoughts cuz this is KILLIN me!

got truck inspected, failed due to emissions. put a bottle of P-90?? in it, ran the **** out if it at 100 mph for about 10 mins, truck was running GREAT! came back and passed the inspection. went home parked truck for about 2 weeks. next time i started it there was a minor mis, a little bit of a shake on acceleration. parked it. tried to take it out again about a week later, shaking and mis had gotten worse. checked egr, all good. checked pcv, all good. started it again and it was now really shaking bad and totaly missing on acceleration (actually backfired on me). noticed that my coil (stock) was making a clicking noise, replaced it with an accel super coil and changed plugs (all looked fine). made a BIG difference in the shaking, but still was missing a little bit and had a loss of power. took distributor apart last night, all looked good. put it back together fired it up and white smoke started coming from drivers tailpipe after about 5 mins of idle.

this motor is tbi, and only has about 6000 miles on it. this truck was running top notch prior to the inspection day. could the p-90?? have clogged something up? oh, i did put some injector cleaner in it and a full tank of premium after all this happened. do i have a blown or leaking head gasket? i dont have milky oil and my coolant level is the same.

what is making this run like ****?? any ideas? i checked for vaccum leaks and didnt find any either. COME ON GUYS<<<<HELP A BROTHA OUT!!

thanks!