VTEC Does not scream as hard as it should

Anyone know where the ecu is located and how to check if there are any errors? are vtec solenoids all the same?

Your ECU is usually located on the passengers' side near the kickplate, it's the panel identical to where your - Hood pop is located on the drivers' side. The VTEC solenoid is more like a switch, if you have VTEC, it's working and if it doesn't activate VTEC it's not working. Chances of that failing is pretty rare. That's all the VTEC solenoid does, nothing more and nothing less.

with the sound it could be the diff air filters or standard air boxes however your set ups are, most of the sound comes from there... try swapping each others setup and see what happens... or various other mods if not the same could cause this...