MTC Motorsport BMW B58 Stainless Steel Downpipe With Hi-Flow 200 Cell Sports Cat and Heat Shield. The B58 downpipe is machined from T-304 high-grade stainless steel and are tig welded in house. This downpipe comes straight from the turbo providing a sharper throttle response due to a faster spool of the turbo. It will provide noticeable power gains and a much more aggressive exhaust note which sounds amazing. It produces lower temperatures and less exhaust backpressure due to the relief of the turbocharger. The cylinder charge is increased which gives you maximum performance. These will fit the following models with B58 engine and pre OPF. We have tested this product and found increases of around 20-25 bhp without tuning and 120bhp+ on a tuned car. Professional installation is recommended as some exhausts sit slightly different from others and can be tight. If you have a later model car with OPF/PPF filters they will need coding out so you will need to find a tuning company who can do this. These should pass an MOT emissions test when fitted.