first off my car is a 89 vert na stock besides an air filter and straight pipe exhaust, all of a sudden in the higher rpms it seems to brake up as if a piston car would be miss firing on a cylinder. i almost curtain it isnt a spark problem. i think fuel is cutting out at 6k rpm or im getting way to much fuel choking it out. im not going to by new injectors cuz im t2 swapping my car next month, can i use 1988 s4 na fuel injectors on my s5?

 

Although both '88 N/A fuel injectors and '89 N/A fuel injectors are 460cc, they are physically different. The '88 fuel injectors will require the use of the square fuel injector clip (Bosch EV1 style), whereas the '89 fuel injectors use an oval fuel injector clip. Also, your current S5 fuel injectors ('89-'91) are high impedance... So IF you do use another set of fuel injectors, be sure that you use S5 N/A fuel injectors or the '88 N/A (high impedance) fuel injectors instead of '86-'87 N/A fuel injectors, as they are low impedance and will require use of the solenoid resistor pack.

As for your current issue... You may have some clogged secondary fuel injectors. They may need to be professionally serviced. You can look into Witch Hunter Performance for fuel injector servicing. I've always had great experiences with them.

You can check to see if the injectors are leaking by strapping/securing the injectors to the fuel rails. Unbolt and remove the fuel rails. (There's an illustration of this in the 89' FSM. "Fuel and Emission Control Systems" F1-56) - Obviously you do not remove the injectors or any of the fuel lines. Be sure to set some rags or something under the injector's fuel outlet nozzle, to absorb fuel in case they are stuck open. Jumper the yellow fuel pump test connector at the passenger side strut tower, near the AFM. Turn the key to "ON"... Not to "START". You'll hear the fuel pump running... Now go check the injectors to see if they are spewing/leaking.

If you do not have a Factory Service Manual, here is a link to the 1989 FSM "Fuel and Emission Control Systems": http://foxed.ca/rx7manual/manuals/19..._non_turbo.pdf

 

Looking at this at another perspective: you are going to swap in a month,correct?
Swapping the s5 injector for an s4 would require a minor hacking of the harness to just put that "odd injector" in.Plus the fact that you would be taking the upper manifold off to do it.
Personally I like things working on my car,But in this case you would be tearing into the car to fix something that will be removed in a couple weeks.
I would just stay out of High revs and swap the engine as intended.That would save labor and cutting injector wiring..then putting the old connector back on.