HELP! Got a high pitched whistle 2000 Cav

I've got a 2000 2 dr cavy. I had a resistor mod for the IAT that I removed,then about two days later I started getting a high pitched whistle out of my engine.
I took it to a garage, where they tried tracing the noise but couldn't find it. He suggested getting my computer reflashed. Now is this going to be one of those things thats going to cost me a whole lot for nothing?
Any thoughts would be appreciated.

Thanks