96 explorer 4.0 intermitten loss of power

[96explorerxlt2wd]

I have been having this problem for a while now. When I'm accelerating my explorer starts to shake and almost feel similar to slipping in the rain. Every once in a while the idles will be rough too. Under hard acceleration the engine seems to hit a governor at 2500 then eventually climbs to about 3000 and shifts. These problems seem to occur every once in a while and don't seem to have any warnings to when it will happen. My engine light is on but the only descriptive code is P0149 "Secondary Air Injection System Control B Circut", the others are P014A, P031C, and while I was driving as it was shaking my light started flashing and gave me P151C, but that and the other two only say no description. I have replaced the plugs with Motorcraft (had autolite and was told they were junk and probably the problem), all the seals from the intake manifold up were replaced because of a coolant leak and all parts were cleaned, has a CAI, cleaned the MAP sensor, cleaned the IAC because of whistling coming from the intake, and compression tested. Anyone have any idea as to what I should check or what is causing the problem? Could the secondary air injection system be an EGR problem? Ford garages tell me the code has to be because of an exhaust pump but I cannot find one. Btw it has 178,000 and I have not had this problem for three months when I changed the plugs and that's the way it's been for the past 5,000 miles but whenever it comes back it's always worse than before.