I have an '89 Prelude with a B20A5 that was installed by the previous owner after he blew the original engine. I don't know what was in the car originally and I don't know if the ECU currently in the car is original, or was taken from the car the replacement engine came from. The problem is that the stupid thing won't rev over 4k. When you hit 4k, it chugs horribly and speed drops off very quickly. This sucks, partly because you can't go over 80, but mostly because you can't downshift to climb hills and such. I recently found a good deal on a JUN Racing BA5 chip for a PK2 ECU. Will this fix my problem? In any event, why is it like this in the first place? To me, it seems like 4k is an obnoxiously low rev limit for any car. Has something gone horribly wrong to make it like this? Is some sensor giving the ECU a bad signal or is it actually possible that the ECU has been set to cut out at 4k?