Hi guys. after a bit of help with this one. As above 1.4 Polo with only 1 fault code 17599 - Long term fuel trim additive air Bank 1 Range 1 system too lean. Fuel trim is showing -75%!! On erasing code fuel trim very quickly returns to this value.

List of tests carried out:
Smoke test inlet system- blank missing from brake servo one way valve. blanked off no other leaks found. Breathing system not leaking / no oil leaks etc. hoses appear clear with a good flow of smoke with hose to air filter removed.

With EGR vac hose disconnected there is a bit of smoke coming from the EGR valve its self? Possible diaphragm failed??? There seems to be valve or conector that is hanging in the breeze and not conected to anything does anyone know where this should go? TPS dont really seem to know. Im wondering if this is the fault or just a red herring!

Throttle body was dirty, cleaned and adaptions reset.

Fuel pressure 2.7 Bar with vacuum and 3.2 no vacuum (Spec from auto data 2.5 Bar with, 3.0 Bar no vac).No fuel pressure drop over hour.

Emissions checked at idle: CO 0.584 CO2 14.03 HC61 O2 0.28 Lambda 0.993
Emissions at 2500 rpm: CO 0.617 CO2 13.93 HC106 O2 0.43 Lambda 0.995.

Wide band oxygen sensor fitted and reading 450mv (must admit not sure on best method of checking these)

Im interested to know where you would check next or any experience in this area.

Many thanks James