For the most part, pipes will 'boost' the power band at the rev range they're designed for. Low end pipes boost low end, high end pipes boost high end; regardless of the cylinder porting. BUT, a low end pipe on a cylinder ported for high revs won't be as effective as a low end pipe on a cylinder ported for the same (low) rev range as the pipe; and vice versa.
Cylinder porting takes "precedence" over the pipe range. You'll be able to rev a low end pipe high on a cylinder with high port timings (ported for high revs), such as a Tecno/Proma circuit on a heavily ported DMP. The Dutchies are getting over 12k RPM out of the circuit pipes, which are "low end" pipes. Conversely, if you were to throw a Simonini (high end pipe) on to a stock cylinder (low end cylinder), you'd never get into the pipe range because the port timings on the cylinder won't let you rev high enough.
Maybe that helps?