Lazy MAF sensor

2005 MK4 BEW. Our MAF sensor seems to be lazy based on plotting the output at full throttle in VCDS. It spikes over 900 then diminishes to under 700 while holding the pedal to the floor the whole time (15+ seconds). Turbo is showing great >2000mbar and boost specified follows boost actual very closely. No codes.

So having nothing to lose, we took the sensor out and tried to clean it. No improvement at all (I didn't have much hope anyway). But I found that it appears to be missing the little diode thingy on the side:



Isn't it supposed to look like this? Or is it different on our model?:



I looked could not find this missing diode looking thing in the air passageways or air filter, so either its not meant to be there or it had fallen out a long time ago. Anybody thoughts?

Oh one other question. I know intake clogging is not common on BEW's since they have ULSD fuel, but has anyone ever really found these intakes to be clogged anyway? Engine has 189k miles. It feels like we have more acceleration at lower RPM's than higher RPMs. I still think the sensor is the issue, but wonder about intake too.

Our fuel economy has been around 32 for a long time now. This is an automatic, but thats still very low. I used to get in the 40s.

Deal with the MAF first. Intake clogging wasn't eliminated with ULSD; but, these engines tended to clog way less (but it has occurred- they're not immune).

If you still have performance issues after replacing the MAF (I'm assuming it needs replacing- someone who actually knows what they're talking about here ought to chime in with real info!) then you're probably going to be looking at the fueling side of things.

Is that the MAF or MAP? It looks sort of like a thermistor that is missing.
Makes sense to have one in the air pathway, so maybe your MAF(MAP?) is lazy for a reason.
But your car was known to have cam wear issues so you should have a look at that.

It's the MAF after you remove it from the air flow straightener housing right at the air filter. I'm just going to pop a new one in I think. I did a little more reading and found this thread that explains the diode is part of the built in temperature sensor and not used on all models:

http://forums.vwvortex.com/showthread.php?4281957-FAQ-DIY-MAFs-fixing-them-to-save-cash.

On the BEW it seems like G72 intake air temperature sensor is part of the MAP sensor assembly so it reads temperatures after the intercooler. My guess is you would only need temperature from the MAF (with the diode installed) on naturally aspirated cars. Seems like I answered my own question, the diode missing is probably normal.

For the camshaft, I have the camshaft on my radar but I checked it last year and could not see any sharp edges on the lobes. I unsure though because the engine was making a hell of a noise at one point like one of the valves was stuck or something. It still makes that noises but more very muted now. History of the engine is known, it came from the junk yard. Might make sense for cylinder head to come off for inspection at the same time as the camshaft job.