ORIGINAL: Pat Roy
Start easy and cheap and work up is about the best one can do. It's a royal pita when methods don't work.
I like the way you think. I had this issue with a DA 50 and never resolved it. I tried many things...even replaced the carb with a brand new one. Not sure it was even in-cowl pressure/drafts issues.....I sold it. Using a ZDZ 50 NG in the same exact plane had no issues at all. It wasn't the cheapest or easiest but it sure worked well. It's so awesome to have a plane with no engine issues.