Im compiling a list of boost controllers that allow RPM based boost settings so that you can help eliminate taper. Feel free to add to the list. That is all.

Apexi- AVC-R

HKS- EVC-VI

Turbo XS- Dtec (requires gameboy advanced)

Greddy- Profec E-01

Turbosmart - E-boost2

World Electronics - TBC-1, maybe PBC-1 also.

Blitz - SBC-color, SBC-Id