The headers on my 2001 DS are glowing pretty good at high RPM under no load conditions so I went up two sizes from a DJ 185 to a DJ195, they still glow bright, but I don't want to change any more jetting until I get it out into the real world, the whole no load jetting isn't too good, but it's a good start I figure. I went from a WB E-Series pipe to one of Mr. HPs Endcaps, so with that minor exhaust change I'm moving so much more air the headpipes glow - the never used to on the E-Series. I'd say that speaks well for the Mr. HP endcap's ability to move air. I've had the endcap on there for a few months but have yet to take that machine out to the dunes...