While outside last night clapping for the NHS, I was speaking with my neighbour about my reversion issues. He used to run a rally team so he does know a few things. We got talking about carb trumpets and how restrictive the airbox is. I notice that my AFR drops by a whole number when I add the air filter. He suggested running without the air-box or filters. Now this is something I am unlikely to ever do for more than a tuning run or webcam recording session as I will twitch with fear every time I see dust being kicked up on the road. But he reckoned that he never had issues running open trumpets and never had to tear his engines down because of foreign objects getting in. One thing is for sure, you never want to run carbs without trumpets. I do like the sound of open trumpets and would as a minimum opt for ITG style trumpet socks for anything long term. His logic was that unless you suck the big debris, it all gets in and out so fast it’s not going to get stuck in the cylinders. But maybe a race / rally engine does fewer miles between rebuilds than a road car to even notice the fine dust grinding the walls!? So this got me thinking about how many people here run their triples, SUs or ITBs with open trumpets and if they have ever had issues. Anyone? Interested to have a tech / logical discussion on this if possible and see where it goes. I am on the verge of experimenting with trumpets to improve performance and reduce reversion, so it’s a topic of great interest but that isn’t the point of this thread. I guess I’m asking for long term experiences or views on open v filtered trumpets.