yep done both mine , you can alter the smoke screw which is under the tamper proof bung on top of the plate you take off. about 1/4 turn c/wise, then remove the cover with the 4 screws you mention , diaphram 1/4 c/wise and under the diaphram theres a star wheel about 1/4 turn or a little less on that any more it may smoke . what ever you do mark every thing step by step so you can put it back iff need be. all this do on your own risk . i never had a prob with mine . but remember iff it smokes it means un burnt fuell which means higher egt which means trouble in the long run so take care ..alan