89formula350tpi

About a year ago my car had a problem, when I started the car it would idle real rough than stall. The SES light didn't come on so I assumed there was no code. I had it brought to my local shop and they replaced the MAF and everything was good. Until today. Today I had the same problem with my car but once again no SES light. So I went and bought a new MAF and put it in and the car ran good except it would hesitate from a stop to about 2000 rpms but after that it ran good. But after about an hour of driving I bring it home and it starts idling real low and rough again then it would stall sometimes. It would always stall if i turned on my heat or a/c when it was idling rough. The new MAF looks different than the stock one. It does't have the thin wire in the middle, it has a circuit board thing running straight through the center. It is a Micro Tech MAF from my local parts store. The instuctions included with the new MAF said it might look different from the OE sensor but any differences where made for better quality and performance. Also my smog pump is making a knocking noise, I think the bearings are going, but I don't think that would cause my problem. The fuel pressure is good, new fuel filter, air filter, plugs, wires, cap, rotor. The motor only has about 5,000 miles on it. What do you think would cause my car to idle real rough, stall and hesitate.