Check the hose clips for tightness and examine the trunking for any cracks or splits and as well as every the vacuum system, the little bore pipes and fittings for cracks and missing parts. The best mannerism to locate a leak is to have the engine running and warm and after that spray can lighter gas /propane or brake cleaner in this area each joint in turn. If the engine rev s up you ve found your leak.
Its in addition to worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not at your best pump will all result in insufficient fuel monster delivered to the engine. Might after that be worth cleaning out the idle swiftness run motor / valve as these acquire clogged happening subsequently carbon and some brake cleaner washed through helps clear things off.
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you taking place to date upon every maintenance; spark plugs fuel filter pcv vlave etc? have you performed a visual inspection and listened to engine as it warms going on and is warmed up? oftentimes in engine produce a result many factors may cause the thesame symptom(s)