[nissanfanatic]

Are these side feed or top feed injectors?

I don't see typical racing fuel messing up your injectors. Most of the higher HP 240sx guys I know run it.

Now that injector cleaner BS is prolly what is messing you up. I'd quit using that stuff. As quoted from RC engineering:

"Chemicals that are strong enough to even clean your injectors would probably eat your entire fuel system,"

If anything, keep a set of backup injectors, send the set that is out to be cleaned, then at some point, pull the injectors from your car, put the cleaned ones in, and send the ones you just pulled to be cleaned.

As for fuel selection, you should run whatever the car runs best on. If it isn't detonating on what you are running now, then there is no point to running higher octane fuel.