Spider injector problem?
 

I have a 99' Blazer that I have been having an issue where the truck feels like it's misfiring but not a complete misfire. I would assume you can easily tell on a V6 if there is a misfire. Anyways when I'm accelerating the truck seems to "misfire" randomly. You can feel it, like a misfire but not as severe. I have done the plugs, wires, cap and rotor and awhile back I did the intake manifold gasket and I also did the Fuel pump, filter and spider injector (Upgraded to the MPFI unit) to solve a hard starting problem. Now I have a random starting problem again and what feels like a lack of power when driving plus I am getting like 200 miles to a tank which is pretty bad. I'm starting to think it might be the spider injector assembly as they cause all of my problems when they go bad. Plus I bought the "Standard Products" brand; the offbrand and that could have bit me in the ass.... The missfire could be an injector or two in the spider not firing correctly? Fuel pressure is good so don't worry about that.

Anything under 50% throttle just doesn't accelerate worth a darn. Only when the truck is cold does it run ok and drive semi-normal, when it warms up I start to feel bumps in the idle and the "missfire I have mentioned"

I also just changed the MAF due to a stored code.

Any ideas? Its REALLY annoying!

Unplug the MAP sensor see if it still does it, if so, get a new one. An MAP sensor is to the left of the spider injector plug and has three wires.

Since you did not mention it, I'm assuming no warning codes?