Check the hose clips for tightness and inspect the trunking for any cracks or splits and furthermore every the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best way to find a leak is to have the engine doling out and hot and next spray lighter gas /propane or brake cleaner re each joint in turn. If the engine rev s taking place you ve found your leak.
Thanks for your response. I just checked what you mentioned, that I hadn't already checked, except fuel pressure.Let me tell you a little more about the trouble history. It currently has a master tech attributed idle let breathe run valve and tps installed. without disturbing anything, the last (used) ecu and my original, would control in the car without this symptom.
afterward I begin the car, the engine surges taking place between 1200 and 2000 rpm encourage and forth. I misused the IAC and the TPS as soon as no correct in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to become accustomed the idle eagerness screw to demean the rpm and it would hold for a while. Now, the engine is continually surging to the point where I cannot drive it for danger signal of damage to the steer train. Any experienced solution?