I have similar screens b/t my airhorns and my throttle bodies but that's it. For when the car is sitting, I also used the tennis balls but I have moved to small round filters I cut out of a humidifier filter
(they look like little biscuts I push into the horn). Again, I only use them for storing the car. I have accidently started the car when they are in and they seem to quickly pop out.
If anyone has any ideas for some kind of "sock" like filter that is heat resistant and looks good, I am in.
Apologies for highjacking the thread Fred...Again the car is AWESOME.
Kramer