call jack he custom builds them to order and has done some nice 3.5 stainless pipes with your choice on the gate and with the gate coming off the header
I bought a 3.5" external DP from Big Wood Racing. Fit and finish was awesome! High quality, and I got it in stainless. I opted for the Turbosmart wastegate to finish off the install. Call them, you wont be disappointed. Hope this helps...-Steve