Well you are experiencing either a cheap part or the engine is letting gas or gas fumes enter the diaphragm. Is your modulator 2 line or single line???? Either way you need a FUME TRAP. I do not know where you can get one Though. They are obsolete by now i would think. Years ago the 360 jeep engine used to blow the distributor cap off the engine. It took me a week to figure it out. The dizzy on that car was lower than the Carb and fumes ruptured the diaphgram. Then the fuems traveled into the DIZZY. When you cranked it over the spark ignited the fumes and blew the cap off. I got hundreds upon hundred of calls about this years ago. People actually thought someone was messing with their cars. Peace TOM:bigthumbsup:bigthumbsup