I'm not sure about the K&N cleaner...it would probably work "ok" on foam...it works awesome on K&N filters as it should....I've used it on my KZ1000 since 1998.
Way back in the days,I would soak them in gas for a few minutes to get all the filter oil and the bulk of dirt off.There was always controversy about gas breaking down the foam and the seams,but all the years I did it,I never had a problem...I've always run Twin-Air. From there,it was ALOT of warm/hot soapy water washes.
Now-a-days(meaning the last 10-12 years)....I just toss the used Twin-Airs right in the trash and throw in a brand new one......sooooooooo much easier and quicker...since I NEVER "enjoyed" cleaning filters.