1990 5.0 having trouble with backfire issue

I have a 90 5.o all stock except complete aftermarket exhaust. hi flow bbk cats and h-pipe flowmaster super 44 mufflers and bbk shorty cermaic coated headers.
Now for the problem.....upon initial startup i have problems with the car bogging down when i give it gas to the point where it almost dies before finally engaging the throttle. and after allowing to warm-up and drive off it wants to stutter thru first and second and backfires and gurggles out exhaust. It only does this the first or second time i row thru gears and will quit and run normal after.
Then when i get to a red light if i am sitting for awhile when i go to take off it wants to act up again and repeat the issue thru second.
I am sometimes even having to rev the engine a little before engaging first gear.
I did a compression check and had 140 in two cyl and 150 in the remaining cyl. one on either side of block had the 140 reading.
Re gapped my spark plugs. wires and distributor cap are both firly new. checked all my vacumns and have no service engine light on.
Still need to check the timing but as of far cant determine what is causing the problem.
Any and all help would be greatly appreciated....thanks ahead of time...lost in AZ:worship