1995 Chevy Blazer Jerking engine?

I have had my Blazer for 2 years and all it has been is a lemon. I've put about 4000 dollars into it. For about a year it has had a problem with jerking at random points in acceleration. At first it would be in about first gear at around 2000 rpms then it got so bad I had to rev the engine at stop signs or stop lights or it would die. I took it in and they said my EGR valve was clogged with carbon and if I didn't want to pay $500 for them to sandblast my manifold they would just unhook it. They did and it seemed to work okay for a while. Then whenever I would accelerate hard it would jerk and sometimes barely move. Sometimes after letting it sit for ahile idling and then try togo it would even stall. If I watched my tach. The needle would just crazy and bounce up and down. My truck ran into other problems with stalling and such and I had my fuel pump replaced some sensor replaced that works with the fuel pump ( I can't remember the name) and had a new egr valve installed because the old one had oil in it. After the last time I got it fixed the guy told me I had a lazy intake valve and to just run a bunch of cleaner through it and it should help if not he said I would need my Spider? Replaced I think I misunderstood what he said but I have run hundreds of dollars and most brands of fuel system cleaner through it and it still messes up not as bad but everytime I floor it from a stop it will and if i'm going 75 down the highway the tach goes crazy. I am sick of having problems with it and just want to get it fixed. Do you think I really need a new spider or is there something else that is wrong that he didn't catch? Or do you have a suggestion about a brand of cleaner that should work in it