Check the hose clips for tightness and examine the trunking for any cracks or splits and as well as all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best pretension to locate a leak is to have the engine doling out and warm and then vaporizer lighter gas /propane or brake cleaner more or less each joint in turn. If the engine rev s going on you ve found your leak.
Its along with worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a below par pump will all outcome in insufficient fuel subconscious delivered to the engine. Might also be worth cleaning out the idle keenness control motor / valve as these acquire clogged stirring later carbon and some brake cleaner washed through helps free things off.
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you happening to date on every maintenance; spark plugs fuel filter pcv vlave etc? have you performed a visual inspection and listened to engine as it warms stirring and is warmed up? oftentimes in engine be in many factors may cause the same symptom(s)