yeah im keeping the cat and stock header for now as soon as xmas is over im going to put race header and flex pipe on i just want to know if i get a custome exhaust put on after the flex pipe will it give me the same gain as a true cat back made for it or is it just going to be for sound only
the gains made by an axle-back (since we have a front mount cat) are because of the loss of restriction and lowering of backpressure. the majority of these systems include a straight through muffler with some utilizing and additional resonator... the addition of a flex pipe lengthens the unrestricted area (also typically a bottle neck since the flex pipe is corrugated to allow engine movement) the use of a race header give an advantage of equal length tuned primaries which aid in exhaust scavaging....also creates a better vacuum pulling more fuel/air into the combustion chamber. the shorty header is used in the same way but attempts to retain the stock Cat location for emission purposes...the use of a high-flow CAT eases up the CAT bottle-neck while still retaining emissions. O2 sensor cheaters are dodads the trick the ECU into thinking everything is honkydory while running with either an off-road pipe (temporary pipe which replaces the stock CAT for RACE purposes and can easily be replaced for street driving...not as effective as a race header) or race header.