I have done a lights out test with them on and have seen allot of leakage traveling to the head.
I think the boots for the spark plug sets are far better now then what came out in the 80's.
These shields become degraded over time and lose allot of their insulating properties.
On top of that the material that’s inside of them cracks and in some cases has fallen out further aiding conductivity.
My 2 cents would be to remove them.
Red 1988 GT 5 speed LQ1 Powered
Poly all around, Koni's and Lowered
Items for sale - cradle support - 3800 tranny mounts