Vw passat 1999 1.8 t has loss of power. Won't go over 40 ...

Vw passat 1999 1.8 t has loss of power. Won't go over 40 mpg. Or over 3000 rpm unless first started. I have replaced mass air flow sensor, the turbo, exhaust and intake manifold gaskets, the fuel filter, replaced crankshaft breath...

Vw passat 1999 1.8 t has loss of power. Won't go over 40 mpg. Or over 3000 rpm unless first started. I have replaced mass air flow sensor, the turbo, exhaust and intake manifold gaskets, the fuel filter, replaced crankshaft breather assembly, changed spark plugs, ran lucas fuel cleaner through it, cleaned top end of motor, tested fuel pressure--55 psi at idle, 60 psi at acceleration, only ran 91 octane fuel and octane boost helps but doesn't eliminate problem. Slow to accelerate, no power for even slightly steep climbs. Was misfiring cylinder 1 but after spark plugs replacement no longer misfiring. Have not replaced air/fuel regulator sensor or fuel sock in tank. Mechanic's Assistant: Is the power loss consistent, or does it fluctuate? Consistent with not going over 3000 rpm or 40 mpg. Sometimes it will surge and at first start has more power then after running even for a few minutes Mechanic's Assistant: Are you fixing your Passat yourself? What have you tried so far? Yes and listed in first message

Automotive Expert
Hello, Welcome to JustAnswer. My name is \*\*\*\*\* \*\*\*\*\* I am an independent Auto Technician. Sorry to hear you are having a problem with your Car, I will do my best to assist you with this issue. A live optional phone call will be automatically offered by JustAnswer, But I can not do calls at the moment we can carry on with text? It may take a moment for me to get back to you as I may have to look up information about your concern, So I really appreciate your patience. Do you have your VIN number handy for me so I can look up your vehicle? If no Vin? then all I need is Make, model, and engine size. May I ask who I have the pleasure of chatting with? Regards Greg.

1999 Volkswagen passat with a1. 8 turbo
Automotive Expert
Hi. Did you check for malfunction codes or did you replace the said parts on assumption? If you have codes did you clear them, then do a test drive and then recheck for codes?

Initially there were codes for large vacuum leak and misfire on cyl 1after replacing crankcase vent system and spark plugs those went away also when inspecting turbo there was wear in bearings and impeller.Codes have not come back after test drive but still low power and can't get over 35mph
Automotive Expert
Turbo was replaced with new or used. What codes do you now have? Greg

New turbo and currently no codes
Automotive Expert
Did you check for transmission codes?

Automotive Expert
Disconnect the MAF and do a test drive, see if it runs better? With the scan tool, go to live engine data check short fuel trim at idle then again at 3000 rpm

Maf sensor is brand new
Automotive Expert
Still try with it disconnected. Greg

Rus the same with maf disconnected
Automotive Expert
No codes then i would pull the injectors and check the volume flow of each injector? Can you get me the live data. MAF at idle then at 3000rpm. Short trim idle then at 3000rpm TPS engine OFF and then with fully pressed accelerator reading.
Automotive Expert
Hi. My goal is to provide you with excellent service so I was wondering if you still needed assistance with this issue If you do need more help, please let me know so l can continue to assist you, simply reply if you require additional information and I will be happy to help with any follow up questions. I am not done until you are happy. ​ Kindest regards Greg

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