I ride a 2006 FLHR with a 95" big bore kit, C&P forged pistons, 590 lift cams, and stage 4 head work done by R&R cycles. I'm running a Mikuni HSR42 with stock pilot jet 1.5 turns out, the stock jet needle w/ stock clip position (middle), stock main jet, and stock accelerator pump jet which ends at 3/4 throttle. I previously rode with the stock header pipes with V&H slipons and the bike pulled hard when I hit 2.5k-3k rpm and it continued all the way up. I recently purchased a Supertrapp Supermeg based the positive reviews and the ability to tune my exhaust to my particular build. I started with 12 discs and a closed end cap and worked my way up 3 discs at a time. Even at 24 discs with a closed end cap my bike bogged down at high rpm. Dropping my jet needle clip down one notch to richen the mixture worsened the issue as did increasing my main jet size. I purchased an open end cap for my Supermeg and started with 10 discs and I immediately gained mid/high rpm power. My bike pulled even harder with 14 and topped out at 15-16 discs (which is apparently outflowing the core anyhow). I find it unlikely that the Supermeg doesn't provide enough flow for my particular build, but I'm surprised that I've lost performance over the stock headers and slipons. Do any of you have any thoughts on this build and the closed vs. open end cap? Or is there anyone who has a similar build that wants to share there input? This forum has been a great resource for me but it seems that it really does come down to each riders particular build. I'd like to get this exhaust nailed down before I dial in my carb.