My ’99 WR has about 1000 miles on it (I wish I could put more on it). When I change/ clean the oil filter, roughly every 100 miles, there is the usual accumulation of metal particles. When I changed the oil and filter this week, I was AMAZED that there was almost no debris on the filter. There were 3 metal particles that I could see on the filter and a few metal particles on the bottom of the filter cavity on the WR. What changed that would so drastically reduce the amount of metal particulate on/near the filter??? As I thought about it, 2 things have changed: 1) I recently switched from Castrol GTX petroleum based oil to Mobil 1 15W-50 synthetic oil. However, this reduced debris phenomenon occurred after the second oil/filter change with Mobil 1. The first oil/filter change with Mobil 1 had the usual amount of filter debris. 2) I installed a BigGun SDS exhaust system exactly one oil change ago. So, you ask, what does a BigGun SDS exhaust have to do with crud on the oil filter? Well, first of all I shift about half as often as I used to – this is probably most significant. Second, BigGun CLAIMS the ceramic coating on the pipe drastically reduces oil temperatures. This may OR may not be a factor. I wanted to share this finding in the spirit of this forum and am curious to hear what others may have observed. Eric in WA ++++++++++ ’99 WR400, YZ timing, BigGun SDS exhaust, Air box lid on without the snorkel, WB air filter, IMS Tank, YZ Seat, Acerbis Handguards, Scotts Steering Damper, Renthal Bars, Devol Rad Guards, Dunlop 755F & 756R Tires ’99 Polaris 400 Scrambler –“Trail Couch, Toolbox and Lunchwagon”, ’99 Honda Z50R, ’97 Honda XR70R, Kubota L275DT and an assortment of farm equipment.