Lost power kicks in at 3,500 RPM?

Hi everyone,

Well, me and my brother were fixing my passenger-side strut tower (was cracked) so we disconnected the spark plug wires & battery, took out the air induction pipes, and moved many of the wires in the way of welding/grinding. (Yes we covered the engine as well)

The strut tower got fixed but now my cars gets a sudden burst of power at around 3,500 RPM, it's nothing BIG but this horsepower seems to have been robbed from me until I hit that RPM because the car seems a bit slower. So does anyone have any ideas? We checked the sparkplug wires and they were all properly connected. All other wires have been connected also. A question I had was whether the welding/grinding could have shot off and damaged something that could have caused this, but what?

Any help or ideas are appreciated, this one has got me stumped.

Well I cleaned many of the electrical connections I've messed with within the last couple days including the MAF sensor but the problem is still there.

I'm pretty sure I'm not paranoid though, it doesn't happen in 1st gear though all of 1st and some of 2nd feel REAL sluggish, but in 2nd it will jerk me back in my seat (like it should) as the RPM's climb at a steady pace and hit 3,500ish. In 3rd gear I think I felt it as well but just not as hard.

Before this problem arose, I had just installed a bigger MAM (76-80mm? kept same sensor, 19lb injectors) and changed the belt, the belt is slightly rubbing against itself (we installed it at night and thought this new belt arangement was good) so could either one of those have effected the car? It was less than a week ago when I did those modifications and the car ran awesome immeadatly after each of those.