The performance seat cut we talk of is cut on a CNC seat cutting machine by PLR engine recondioning in Brisbane.
Long story short, it basicly puts the seat out into the air stream, or to put it another way, the seat sticks out.
also the topping and tailing is radiused unlike a conventional seat job, where the topping or tailing is just 1 or 2 set angles.
The effect from this, is a creation of a venturi at low valve lift that generates air speed.
It has been tested and proven on both a flow bench and dyno with various engines. As an average, a 2.0 multivalve engine produced 20 extra hp with nothing extra done.
Tony's Corolla had it done and Marus Swart's S2000 VW polo had it done, with suprising results. both came on cam a lot lower down and an increase in mid to hi end torque.