Part ID

Been having some trouble with the 2001 Golf TDI going into limp mode. It seems to happen just after car warms up and when pulling moderately to hard, especially uphill. Can turn engine off and restart and car drives normally again. My son suggested vacuum issues, possibly turbo system. I was looking over the vacuum lines and found a part I can find no information on.

The part number, j10906627a, and the part appears to be a switch or sensor. It has vacuum on the top half but appears to have electrical connections on the bottom. Its located on the firewall, not too far from the vacuum pump. The only websites I find when I run the number are, I believe, in German. The part number does not come up on the 3 VW parts websites I tried, so I was wondering if anybody could help identify it.

Thanks

there is 2 valves mounted on the firewall, the N75(on the right) and the N18(on the left) N75 is for the turbo and the N18 is for the egr. The orientation I gave is if you are looking at the firewall.

Casey823 is correct.
There is a vacuum hose from the turbo actuator to one of the two.
Before you start throwing $$$ playing lets try this next do you have VCDS to scan the car?
It can get expensive real fast.

Had similar issue on mine...Turned out to be a bad MAF sensor. Best thing to do is to scan for a code first then go from there. If you get a P1556 code - really common (charge pressure control - negative deviation) then usual culprits can be N75 valve (previously mentioned), the actuator on the turbo or a bad MAF. There's a great step by step troubleshoot process in the TDI 101 section. As Wonneber mentioned, scan first as throwing parts at it is not the right way to go.

Replacing the vacuum lines, white T connectors and Y connectors, and black and white check valve can be an inexpensive way to fix limp mode. When replacing the lines take one off at a time and replace.

Does the exhaust put out black smoke when you floor it and in limp mode? That would indicate a boost leak. Check all hoses between the turbo and EGR for cracks and loose connections.

If it were a bad MAF you could check it by unplugging the connector. It should always be in limp mode with it disconnected.

Sticky VNT will do it too. My 03 must have been in reduced power mode for a long time due to a bad MAF. Once it was replaced, it started getting overboost limp mode. Everything checks out but the VNT takes more vacuum to move then it should. I will try the oven cleaner method then pull it if needed (have a spare).

Thanks for all the suggestions. I haven't had a chance to replace the vaccuum lines but that was the first thing I was going to do. The MAF sensor went bad several years ago with same symptoms and new one fixed it, but this time that was not the problem. I wasn't going to replace any of the valves prior to replacing vacuum lines and checking the vacuum, but when I couldn't find reference to this thing I was curious. I knew someone here would know what it was.

Hope this thing has a way to go as it is a 2001 with only 187,000 on it.