V-tec problems/engine bogs down before redline

hey everyone. i'm new to the forum and hope someone can help me out. when i try to utilize the v-tec (which we all know was the reason we got our preludes) the engine acts normally until it gets to about 5 and a half. then... nothing. it just continues, until it almost gets to redline, then stops and bogs down as though i'm redlining it. it has nothing to do with the oil, or oil pressure (I don't think) because i tried it right after getting an oil change.

things you should know about the car: it's a 1998 5 speed type SH, with a (necessary after purchasing, fuck you to the guy who sold me the car) engine swap. i THINK, but am not sure, that the engine is an H22A from a Canadian accord. it's a red top. after the engine swap, everything went well... at first. then the VTEC stopped working. also, after the oil change, the VTEC would work shortly, then stop. it also worked after my mechanic monkeyed around with the carburator a bit. it also works (very very seldomly) spontaneously... can anyone help? has anyone ever had the same problem? thanks so much for reading!

Might be the ECU. EDM engines require a different ECU I think. Might be a fuse or relay as well. I'd bring it back to who you bought it from and go crazy.