on my 91 n/a FC
Would having 4 additional grounds that are 10gauge wire be overkill for the electrical system? would there any problems with the car ? starting or running.

 

No.

 

no but it would make your engine bay look absurd and not accomplish anything. The main ground you need to be concerned with is the one under the UIM. Clean the crap out of that. You can run an optional ground by the ECU, but you really don't need any additional grounds added except that one and maybe another battery ground directly to the frame. The other thing to do is clean the battery ground at the long starter bolt. Look at Aaron Cake's site about all this.