sometimes trial and error. The guages have been my BIGGEST error by far. Started w/ stock, then went to the NRAuto's which were high quality BUT I didn't how they looked at night. Then I applied the indiglo's over them, have been very happy with them except for the relay issue. Hopefully this will completely take care of the problem and I won't have any hassle. Again in the future if I get another Z or any car for that matter, I won't mess with the fragile guages. (except to put alum. rings on)