wonder if anyone had APEXi N1 catback exhaust fitted on their E4?! i've actually placed order for one (arriving from APEXi Japan in 1 month time) and will decat using 3 galvanished-steel straight pipe with custom flange on both ends (is this ok or must i use stainless-steel material?!). as for the downpipe, will do it at a later stage coz' i wanna feel the difference with this stage mods first. how does this N1 sounds on our turbo E4, better than HKS Hiper/Dragger or Trust Power Extreme II?! i'm looking at something with deep rumble (at idling), loud at mid-high rev and sounds steel solid!! what sort of bhp/torque increase should i be expecting?! hey, this N1 comes in 1 piece setup only... surprised!! specs: 65-70-75mm mandrel-bent pipe, 160mm muffler unit and 115mm tip.