99 Blazer problems

I am having problems with my 99 Blazer 4X4 LS. It has 142,000 miles. It runs good until you hit about 3,500 rpms then it falls flat on it's face. It makes a kinda strange crackling noise. When I bought it the guy had just put an new transmission in it. It dogs out at 3,500 rpms when taking off & also when you get it down to pull a hill. I have put new plugs, wires, distributer, & fuel filter on it. I also ran some fuel injection cleaner through it. That seems to help a little, but it still didn't do much. I hooked it to the computer & it showed mass air flow sensor. Changed the sensor then reset code. It is still having the same issue. Any idea's?

You hit all the main culprits I had with my 99 Blazer when it fell flat on its face. My problem primarily related to the MAF sensor. The only other things I did was replace the distributor @ 158K miles (the gear was worn) and check/change the catalytic converter (it was plugged). The converter made a huge improvement in horse power. I've read a lot about people have problems with the spider??? in the fuel injection system. I'm not so sure that would only be a problem at high rpm.