I'm not really sure about this by any means but here is a theory:

What type of gas are you using? GSRs are made for 92/93 but you can use lower grades because the computer will adjust the A/F ratio to compensate, maybe by efing around with the sensors the computer isn't able to pick up on detonation.

is there any junkyards around where you are? it should be any more than $20 for one of those sensors, and I would imagine it is just some sort of inductive type sensor so it shouldn't be any worse for the wear.