I have a 97 2door 4wd blazer w/ 210,000 miles on it. I was having problems with what was thought to be the spider injection or the fuel pump. my blazer would bog at certain rpms and i could only give it quarter throttle. this may not work anytime, but what fixed mine was a bigger fuel filter, turn the fuel pump voltage to 12v and put a bigger fuel line on it. it even fixed the whine i got from the fuel pump. now it runs great, you would never guess it had over 200,000 miles. hope this helps!

 

What do you mean by "turn the fuel pump voltage to 12V"? System voltage with the engine running should be somewhere around 14V...

Sounds like you had a restriction in the fuel line...