..the RB 2659 is the same of the Nova 2652 in the inside.
If you want more bite-power you can buy a Nova 2660 or a Capricorn 2662
This 2 pipes has almost the same internals and the same conical tube.
Max's 2664 also has the same components but an "old style" tube. Infact this pipe mounts a traditional 8mm tube (this is the external diameter) instead of the 10mm (Cap and Nova) but it is also conical. Obviously less conical because of a mesure issue but conical
If you want to try something different I can suggest you to buy a Jp-Gimar (HIPEX) 2654. I used this pipe (in combination with MaxPower XXL3 bl) in the last round of the Italian Championship.
I race in the F1 cat. and I managed the final with this pipe.
I also tried a Nova pipe in the previous race days but I choose the 2654 because of the consuption. With the Nova pipe I can't do 5 minutes with a tank but using the JP I did 5.20 mins.
..and the power its the same
(ps:ever used a medium conical manifold)