Idleing very rough

I have a 1994 Altima GXE with the ka24de.

Problem: It idles very rough at times, other times it's fine. Usually around 7-800 RPM but when rough it goes up to a grand and back down to like 700. It also accelerates a lot slower then when I bought it about 6 months ago.

Recent repairs: Recently attached downpipe completely to headers because it was off making the car very loud for several months. Just put in new plugs and did wires, cap and rotor about 1500 miles ago.

Any ideas are much appreciated. Thanks in advance.

Figured it out, I decided I was going to clean my MAS to see if that was the problem and somehow the tubing came loose and that is why it was running like shit. One clamp nut tightened and about 40 miles later car acts normal again. :)