i just finished putting together my buddies LS vtec in his 92 civic hatch. the motor runs fine actually really dips lol, but after driving or having the car on for about 10 minutes or so the check engine light comes on for codes 21 and 23 (vtec solenoid spool valve, and knock sensor) but even after the light comes on the car still runs fine and VTEC's all the way to 8200 without bogging (without knock sensor the car boggs like crazy) what could be wrong and why are these codes coming up out of no where....any help would be greatly appreciated, thx