Honestly I don't think that a filter will hinder or help tuning. As long as you keep your filter well oiled and clean you won't have any problems with the stock filter. I don't think that $20 is worth it, thats just my opinion, I'm sure others will think differently. I had a motosaver on my rc10gt and it died after a gallon and a half. Since then I've had 3 .21's and have 4 gallons in one, 3 gallons in another and 1 gallon in another, they all have great compression and haven't had a problem with regular filters.