I’ve got a 89 wagovan that’s B20 swapped. It runs great but if your at full throttle around 4500-4700 it will act like it’s hitting redline and I have no idea why. It’s a B20b block and a B18a1 non vtec head. Idk what ECU it ha but it’s not the factory one. If anybody can help me with this it would be very much appreciated

 

Unless you have an MSD ignition box or something similar, the rev limits are set within and controlled by the ECU. If you don't know what ECU you have, that is the first place I would start. Once you have the type, a quick google search will tell you the intended purpose is for that ECU. You probably also want to crack the top off and see if it has been chipped.