No boost with running issues after matrix replacement

[220bhp]

I got the car back today, after having quite a lot done.
Heater matrix replaced, diff switch replaced, wiper motor replaced dash bulbs replaced, rs2 bumper realigned {don't ask] and its running like sh??
Mechanical boost only, and hard to drive in traffic at anything below 2000revs.
Revs unsteady and with bad throttle control .
I really think this car hates me. as its mot and tax time at the end of the month an, I cant take it running like this.
I am wondering if any thing could have been disturbed that would make it run so bad.
Any Ideas would be appreciated.

[SteveH]

I would check vac lines/pressure test and VagCom it for error codes. Could be lots of things unfortunately. Who did the work for you? Perhaps you could ask them what they touched along the way.

[DEREKCO]

Definitely check the boost line to the ECU it runs behind the matrix

[dr.strangelove]

Are you sure you bled the system right? Might be an issue picking up coolant temp at the sensor at the back of the cylinder head. Of course, also check on the items mentioned by the other members.

[newsh]

Sounds like a boost leak to me

[fish]

I would start checking the hose that runs to the map sensor. Runs up behind the dash and in to the ecu.

[220bhp]

I can get hold of a mityvac today to check the vacuum line to the ecu .
Also do a boost leak test.
Its not so much the lack of boost .which is a problem that I have had before but, more the poor running at low revs .
last time I had a similar problem it was the lamda playing up , but the new bosch one has not done that many miles . temperature sensor at the back of the head was also changed.

[220bhp]

I tested the vac lines and, may have found the problem.
ecu line and fpr line hold vacuum but , the line that go's to the pink hard line and, T of to the dump valve wont hold at all.
I tried the line to the dump valve and , it still wont hold. the pink line also wont hold.
The dump valve is a forged one .
I will need my snow suit to get under the car and fix it before I know its the cause of all my issues.
What happens if I block the pink line? my difflock doesn't work anyway.

[newsh]

Look under the back seat and see if the diff line has come detached there, there's a rubber T piece and a one-way valve.

Otherwise you can plug it in the engine bay.

The Forge valve doesn't have a diaphragm, it's a piston type, you should get vacuum on the small line though. Quite often the small line to the DV rubs through on the back of the headlight.

Or maybe the DV is jammed open?

I would take the Forge out and fit a stock DV, the uprated one from the S3 is available quite cheaply.

[Rusty]

Forge valves can be rebuilt if there's a problem. I've run one for 12 years with no issues.

On the ABY the DV runs off a dedicated vac line that's on the front of the inlet. Is it different on the 3B? If it's going to the inlet, you'll not get vacuum, so best check if you're bot sure.

Just get some vac line off ebay and replace it all. Use small cable ties to ensure a good seal. Can run test lines to the fpr, dv and ECU to check it out.

[220bhp]

I remove the dump valve , but couldn't find anything wrong with it. cleaned it ,checked the integrity of all the vac lines and, they all hold vacuum.
The only thing I can think is that the dv was stuck open and removing it caused it to free itself as the car is now drivable and, runs a lot better, apart from the fact there is still no boost, only mechanical boost .
Tomorrow its booked in for an MOT.Then I will have a go at pulling the codes.
At least I can drive it to the test centre now.
Thank for your advise chaps . Much appreciated .lets see what we can achieve tomorrow.

[newsh]

Maybe the DV had moisture in and was frozen?

Disconnect the MFTS and see if you get your boost back. And check the WGFV is plugged in.
You can test the WGFV (N75), put a finger on it and blip the throttle hard, you should be able to feel it clicking.

[220bhp]

Ignition on or of for that last one john

[newsh]

Ignition on or of for that last one john

Engine running