Just received from Japan and installed the HKS downpipe was pretty upset as I realised only after I got it that it replaces only the rear main CAT and not the pre CAT. Also not happy with the performance gain from this mod. I have to now fabricate a pipe from the exhaust manifold to replace the pre CAT. A real bummer!! Will elimenating the pre CAT make a big difference?
I hope you didn't wait long for that HKS pipe. I have a used one sitting in my shop with the O2 flange already added. I get those pipes cheap from NOPI, it's a shame they 75mm and only replace the main cat. But they will bolt right up to a Random Tech High flow cat DP.
Received it in 4 days from Japan via Express Mail Service cost me 230$ landed I just realised that my mechanic can get the entire downpipe fabricated for less than 150$ in stainless steel. I will now be making the small custom downpipe to elimenate the pre-CAT. God why did'nt I think of this before I ordered.