I use a Pipercross race filter on the 10, and found them very very good, had used them prior as well, but this was the 1st race filter.
On the box they claimed in their speil about HP gains, with the filter i bought, they say 4.5/ 5.5 HP gains, it was going on the dyno to get the map clearned up, so a run was done to get a graff, then filter fitted and back on dyno, map redone... gain 1.5 HP... thats with PC3 and pipe with cat bypass.... so did i notice any diff.. of course not. be are so easy to clean and put back, well worth it i think.
But on that note, we got 1HP extra with the cat bypass fitted, and tristan got 5 HP net gane by somethings he uses to do when he was building race engines for staford. so all up for very little expence u can gain say 7/8 HP, which is a good gain i think

and with a TRE fitted u get a sharper throttle from closed ect, so that gives u a good sharp engine for bugger all, so thats got to be good
