94Cobra97

I have a stock 94 Cobra and am looking to add a few relatively minor mods (exhaust, underdrive pullies, cold air intake). I was told that modifications may not result in any performance increases as the onboard computer will essentially negate any new inputs. Specifically, I was told that the computer will retard the timing and unless I replace the computer, I'm throwing my money away. I find it hard to believe that this could be true but wanted to check before I throw down the credit card!

Any assistance is appreciated!