Evap vent solenoid will come on if your gas cap isn't tight...seriously.
Forget about that one...and it could be removed from the car and cause NO issue other than a CEL (or in your case, SES...they are one in the same).
For the Knock sensor...they are known to go bad, but it's rare on S14's with less than 150,000 miles.
Did he reset the codes, or is the light still on?
If he did...then forget about it until the light comes back...if it does at all. LOTS of things can cause a SES light, with no real problem.
If he did not reset it...do this first:
http://www.ka24development.com/ecu_codes.html
Then report back here after a short drive.
- Brian