05' BEW Poor fuel economy

Hello all, I have a 2005 auto BEW jetta wagon and the fuel mileage has dropped considerably in the last year. We have replaced the camshaft, lift pump and I have checked and re-checked the timing, but the fuel mileage (Pen and Paper) has dropped from the mid to low forties to around 31 mpg. The only clue I have is that the engine seems to surge at high rpm, like the engine is missing or the air charge is leaking out, but the hoses are all fine to the air inlet. I have checked the operation of the turbo and it is recieving vacuum and making a full sweep of the vanes. Could a plugged intake cause these problems? Could injector adjustment cause these issues? Weak valve springs? MAF? I have a Vag Com and I do all my own work. We have a friend with an 04' that has experienced the same problem. Any input or personal experiences would be appreciated.

With mileage that poor, unless you have a seriosus drag in the transaxle or brakes, the engine would have to be overfuelling grossly, as indicated by black smoke.

Disconnect both the egr valve and throttle plate electrical connectors (this keeps the EGR valve closed and the throttle plate open and eliminates their, or related system, malfunction as an issue) and run a tank of fuel through the engine and record MPGs again. Also, make sure the throttle is open (remove the intake boot from the plastic charge air pipe and look into the throttle housing to verify the disc is open. Running with these connectors unplugged will not cause any drivability issues at all.

After the test reconnect the connectors and clear the CEL codes with your VCDS.

You can also check and log with the VCDS the requested vs actual air and boost and possibly fuel. This may point you in the right direction.

--Nate

I doubt if a clogged intake would be a problem on a BEW. How often do you run the A/C? Are your tires in good condition and properly inflated?

Thanks Nate, I am going to log the maf and boost tonight if I can. No black smoke, not even a problem when the cam was shot with holes in the lifters and the lift pump was only tinkling a little.

JBO5, I live in the durty cackalacky, ac is always on, but mileage is much worse than last summer. Tires are brand new michelin mxv4's inflated to 42 psi all around.

BTW the wagon has 220,000 on the odometer.