Have replaced both O2 sensors, Fuel pump, IAC, MAP, TPS, cap rotor plugs and wires have less than 5k on them, new injectors (99+ style), new intake gasket, new head. When it start this thing up It just runs terrible, sounds like its got a big lumpy cam but then evens out and stumbles here and there after a minute or two. No CEL or anything like that. Ive even tried taking it to mechanics and they've been no help. Any ideas? Thank you!

 

Replace your fuel pressure regulator. Mine had rough starts and even worse after using the vehicle for a while ... after FPR replacement those problems were gone