That is not a very big range, and I know form experience, if the TPS does not read well or read at all, the computer will revert back to standard setting and will basically sit at that. I drove mine like that for a long time. It sounds like the scenario I had on a suburban I bought from some a**hole. He had a 383, built by his meknik buddy, and the mismatched the heads to the block and it had a stuck valve. Would start just fine, idle out of the drive way and up to about 25 but after that when you put the gas pedal down, engine would cut out, but come back to life after you let off the pedal. Took several mechanics to find out the problem. Last mechanic we had it at did a leak down test and found the problem. Check o2 sensors, those go out, and I have purchased several bad ones from autoparts stores. And make sure everything is properly hooked up, I personally love the TBI on blazers, having owned two with it. Fix this 350, and save some money for other things to put into it.