Checking timing 94 5.7

I have been told that to adjust the timing on the 94 5.7 there is an electrical lead somewhere that has to be disconnected for an accurate reading. Can someone tell me if this is true, and if so where is it located?
thanks.

On my old 94, it was a brown wire with a black clip connector that was under the heater ducting in the passenger footwell. (if not there, I have also heard of them being under the black cover on the passenger side firewall in the engine compartment. still a brown wire with connecter) If you don't disconnect it, the timing mark will show way off the timing teeth. I used to set mine at 2-4 degrees after unplugging the timing wire. Good luck.

Thanks! I'll check that out today. :)