Msd Checkout.

I've had my car since new, and did mods back in the early 90's. Gets about 500 miles a year now. Last two years, I'm getting what I think is some detonation when getting on it. When audible, I lift right away. I'm thinking maybe the MSD could have taken a dump? Is there anyway to diagnose it? It's a 6AL with a Vortech Boost Timing Master. I have it set at 3. Edelbrock heads, GT-40 intake, 42lb, fairly mellow cam for boost. 65TB and a Pro-M Mass Air. It has a S-Trim. Remember those? Thanks.

Plugs were replaced about 20 miles ago. They are also the proper heat range. The ones that came out were a beautiful grey color with no spotting. Those plugs were in there since '93 with about 20K miles on them.