i just got a 91 240sx it has the ka24de and no hicas or lsd, does not smoke and starts fine when it idles how ever i can hear a small poping sound under the hood and the motor moves a little it runs great under about 4000 rpms like when i am in town.. but when i get on the highway its bogs down and does not get up past 3200.
what it is doing is back fireing through the engine and sputering on take offs after it reachs running temps.
heres my ideas: bad converter,bad exuast,bad injectors,bad throttle body,burnt valve/s
any help will be great