97 F150 4.6 impossible vaccum problem!!!! -- automotive help

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Subject: 97 F150 4.6 impossible vaccum problem!!!!

Author:
Fred Boss (HELP please)

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Date Posted: 19:59:49 01/25/07 Thu

'97 F150 4wd 4.6 Triton. Initially started missing at idle when warm. In neutral or slight acceleration would make it disappear instantly. Progressed to same missing when started for 5 secs. dissappear instantly. Very low power and fuel economy.
Will set a lean fuel code bank 1 90% of time. Some lean bank 2, some rich codes. Will not set code until warm, shut off, and restarted.
Have had fuel system gone through, new EGR valve, PCV, intake manifold gasket done, new plugs and wires. Exhaust system w/catalytic converters in search of this problem.
Mass air flow sensor cleaned and producing fluxuating voltage within range. Evap relay has power & continuity, no vaccum to tank out of valve when truck warm. EGR vaccum regulator has proper resistance. DPFE? sensor for EGR has proper output voltage.
Replaced intake air temp sensor. Runs far better when unplugged. Runs better temporarily if fuel press. reg. return line to tank blown out, or vaccum line to reg. disconnected. Assuming these are helping richen mix.
Also, heater in cab will revert to defrost under hard acceleration or load. Assuming this is sign of vaccum problem. Sequentially blocked off single lines with little change. Did find one broken line to vaccum reservoir on battery box, no change when replaced.
I'm out of ideas. Anyone have a vaccum diagram or know where the two vaccum lines go through the fenderwall next to the battery that are connected to the EGR vaccum relay and EVAP relay go. The line to control the heater goes through the firewall into the cab through a different route. Can't hear any leaks with hose. Reservoir holds vaccum, can't find anything on lines to 4wd actuator, no change if block line to heater control. Anyone got any ideas?
Any help including psycological referrals would be appreciated at this point.

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