Does the GSR have a RISTRICTION PIPE after the CAT???

If anyone could kindly tell me if the GSR have a Ristriction pipe after the CATALIC Converter. And is it TRUE that if you put a STRAIGHT/ TEST PIPE on the stock exhaust that you will lose alot of POWER??? And my last question is since the GSR has alot of power in the 3rd GEAR....is it better to have a 4-2-1 or 4-1 HEADER????

well, when racing, the only time your at the low end of powerband is beginning of first so 4-1.