I have a strange hesistation issue. Actually there are 2 problems. I have been looking on here to see if I can find this problem. I haven't seen it listed anywhere.

The first problem is an off idle stumble. If you feather the throttle and take off its not too too bad. But if you take off in a hurry you can really feel it. Once it hits about 800-900 rpm it goes away then runs great. The truck pulls great and has a beautiful idle.

I have done a complete tuneup, wires, plugs, cap and rotor. I didnt find any noticeable play in the distributor.

The second problem it has is a chug? or a miss at highway speeds. It runs perfectly no missing until you start to go up a hill. Then once you push the gas pedal down to the point where it's almost going to downshift thats when it does it. It's strange. Once it downshifts it's perfect again. It's been doing this for a couple of months now. I recently replaced the fuel pump, it was doing this before the pump replacement. I also have put a new fuel filter in.

It's not throwing a code. Maybe some one here has had this issue. The blazer is all stock under the hood, I did swap out the MAS but it didn't help.

If you take off and floor it, it runs perfectly, after it gets over the off idle stumble.