Generally speaking, metallic substrates are more durable in relation to the ceramics in terms of holding up against heat cycles, breakage, vibration etc. and therefore can be thinner (have less cell wall) than their ceramic counterparts and thus reduces backpressure and/or weight. They can make more power given constant conditions, however, they can cause more serious boost spikes unless they are specifically tuned just like every other dp. Ceramics are cheaper though.Ultimate racing lists 2 different catted downpipes on their website for th 2008 WRX. Is there any major difference between the two? There is a ceramic version that is 0.00 cheaper so i'm wondering why i'd spend 0 more to get the metal substrate version. Has anyone tried either one on a 2008 WRX?