1999 blazer 4.3 bog with acceleration. new pump, fuel and air filter, fuel regulator. Revs up fine until its put in drive. It will bog a little at first and get worse quickly. I have to baby the pedal to get to speed. Until it's so bad I need to pull over and shut it off for a few and start all over. ????

 

This is more to give you a bump then me having any clue what's going on with your truck.
I would start with a can of throttle body cleaner and a can of MAF sensor cleaner. Get every thing cleaned up upfront and see what happens.

 

It could also be a plugged catalytic converter. If your truck is/was running rich it could have fouled the cat, or caused it to start breaking down. You can test this by removing the upstream O2 sensor and driving with it out. If the problem gets better then you know you need to replace the cat.

 

When was the last time you did a complete tune up?