Need help, car in limp mode.

[Emperor_Tha]

For about a week now, my car goes into limp mode randomly while driving. It happen 2mins while driving, 15 mins, 1hr and so on. It just happen whenever even if I drive like a oldlady or aggrassively for a short time or for while, then it goes into limp. While in limp it's hard to accelerate, exhaust gets loud, I get a lot pop from the exhaust and now I'm getting only 15mpg when I should get 24-26. I have a 89 s13 with a black top with e5 ecu. Everything has been running fine for the past 2years 80k miles since start up. I had a s14t28, safc andz32 maf plus all the basic fmic, hard wired fuel pump. I had swapped out different maf. Stock sr and sohc maf with and with out the safc install. Replace knock sensor, reading 2.5v at idle. Hit the block with a hammer and the voltage goes up a little. Replace the cts, wiring is good cuz the fan works. Had my base timing check by import intell and it's perfect on the mark from the factory. Replace 3 different bov, redid intercooler piping and seal the end with silicone gasket. Still goes into limp mode.

What can be the problem. I can't pull the code becuz it's a e5 ecu with a sohc wiring. I don't have the consult port likethe dohc. I believe I have to jump a few wires like the j4 ecu to pull the codes