I am running the HPI MT2 air filter #87207:
http://www.hpiracing.com/products/en/87207/
It was one of the least expensive dual element filters I could find. It fits, but I had to stretch the rubber boot over the carb pretty tight.
http://www3.towerhobbies.com/cgi-bin...7207&search=Go
I am wanting to try one of the AE SC8 filters. Also inexpensive and I think it should fit the carb perfect. If anybody knows better, let me know.
http://www.amainhobbies.com/product_...ducts_id/16918
For what it is worth,
Spiro