Just a point that may be of interest...
When I purchased my used 2004 EC300 it was fitted with some unknown brand foam air filter. I'd washed it and oiled it a few times and it seemed OK, but just OK, the fit didn't feel that snug.
Yesterday I fitted a new Twinair foam filter, part number 158056. There is a big difference, it really feels much better quality and it's a real tight, snug fit. I don't feel worried there might be a gap where dirt could get in.
From now on I'll only he buying Twinair foam filters.
By the way, I'm still using the stock GasGas plastic frame/cage.
All the best, Dave.