Ive had this problem and to some extent still have it.

To start with ive had the Anti Stall valve replaced as my old one wasnt working.

This valve counter acts your revs dropped rapidly ( like when pulling upto to a junction ) so the revs fall at a more gradule pace and dont cut or bottom out.

Ive also around the same time had some popping from the exhaust altho not anything totally major , usually on the overrun after giving it some revs. Tried presure testing the exhaust and not found any air leaks , and the engine was set up fine , was surgested it could be an air leak on the master brake cylinder , altho as a cure ( temporarily maybe ) ive turned my idle speed up to compensate , to be honnest the problem hasnt gotten any worse over the last 6 mths + so im quiet happy to run like this , the idle speed is set at 800-1000 rpm ( ideal is 850-950 i belive ) when warmed up which is only fractionally higher than normal so no major concearns

Hope some of my rambeling helps ! ... turn up your idle speed