I have WT324 on 2 Homelite 30's and a Ryobi 28. The Homies swing 17-8 7800+ rpm the Ryobi 16/8 7500+ with mag ign.. But I have opened up mufflers on all. Just cut out the 1/3" ID pipe and put 7/16"(you do have muffler on it don't you?) , or for testing you could just leave the hole. The stock carb for 31 Ryobi is WT434. You could try that or any of it's 8-9mm venturi cousins (stock trimmer carbs) to isolate intake probs, but I've never had good luck running oversize carbs with stock exhaust, and never had the same symptoms twice. Just unable to tune the thing. Yea -let us know how you make out.