It sounds like you are running a lot of material during your runs. Several hundred grams and only yielding a small percentage... I can't imaging you running 600+ grams of nugs and sugar trim. For the numbers you are listing I would conclude your material is not refined enough at all. You must be running pretty much everything, stems in all to get those results. Only lower nugs and tight sugar trim is good IMO. You have to get rid of the garbage. (either that, or your tube/filter/butane setup is severely flawed). What size tube, what kind of butane, how much butane are you running per oz?