I've been using fine wire Champions in my IO-360-A1A for 10 years. I don't run LOP because Lycoming does not endorse it. I run 100 degrees ROP during cruise as I was taught by my instructor in 1980. For precision, I use the "Lean Find" procedure using my JPI. I've had not issues, at all, with run-ups or any fouling during my entire ownership. Note: I ALWAYS lean the mixture during TAXI (screw out 2.5 finger joints or just shy of engine roughness) so extra fuel will not gather during the taxi period. Every annual, I rotate the top plugs to the bottom. I take a fine wire and scrape out any goo that gathers in the bottom plugs (which is normal behavior due to any oil in the chamber settling due to gravity) and check the gaps. IA says "keep doing what you are doing 'cause the engine is in good shape and the plugs are not showing any fouling". The fines wires are the way to go. Even though they are $100 each, the peace of mind knowing your aircraft is using the best is quite good....
Hope this helps.
Sincerely,
Carter 6460Q M20F www.goairplane.com