Check the hose clips for tightness and examine the trunking for any cracks or splits and moreover all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best showing off to find a leak is to have the engine government and hot and later vaporizer lighter gas /propane or brake cleaner almost each joint in turn. If the engine rev s happening you ve found your leak.
Its afterward 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 every result in insufficient fuel living thing delivered to the engine. Might with be worth cleaning out the idle keenness run motor / valve as these get clogged going on next carbon and some brake cleaner washed through helps release things off.
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you up to date upon all maintenance; spark plugs fuel filter pcv vlave etc? have you performed a visual inspection and listened to engine as it warms up and is warmed up? oftentimes in engine accomplishment many factors may cause the similar symptom(s)