A4 Quatro 1.8T MissFire on all 4 Cylinders

[Kite.Surfer]

I bought this 2005 A4, B6 with 65K miles... It had been sitting somewhere for a long time. So I have had some of the typical problems to deal with.
When I was driving home in slush, I got very rough idle with large variations in RPM with the system trying to compensate.
It seems like when it is wet, raining or slush.... I get some intermittent problems.
Here are the VAGCom faults.... Hoping that there are some common problems associated with wet weather....

11 Faults Found:
17700 - Map Controlled Engine Cooling Thermostat (F265)
P1292 - 004 - Open Circuit - Intermittent
18032 - MIL Request Signal Active (Check TCM for errors too!)
P1624 - 008 - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - Intermittent
16685 - Cylinder 1
P0301 - 001 - Misfire Detected - Intermittent
16686 - Cylinder 2
P0302 - 001 - Misfire Detected - Intermittent
16687 - Cylinder 3
P0303 - 002 - Misfire Detected - Intermittent
16688 - Cylinder 4
P0304 - 002 - Misfire Detected - Intermittent
17887 - Brake Boost Vacuum System
P1479 - 008 - Mechanical Failure - Intermittent
17544 - Fuel Trim: Bank 1 (Add)
P1136 - 001 - System too Lean
16555 - Fuel Trim; Bank 1
P0171 - 004 - System Too Lean - MIL ON
17519 - Oxygen (Lambda) Sensor Regulation: Bank 1
P1111 - 002 - System too Lean
Readiness: 0000 0000

[old guy]

Most of your symptoms could be explained by a vacuum leak. Thus the misfires and lean codes. Be sure to check the SJP (suction Jet Pump). It is a common failure component and will result in misfires, low vacuum to the brake booster and a high fuel trim. The thermostat code is a separate issue. The t-stat has a heating element that allows the ECM to open the t-stat sooner than the mechanical opening under certain conditions. That code won't cause misfires but ultimately should be addressed before the warmer weather comes back.

[lyates1987]

^^sounds bout right. My suction jet pump came apart resulting in a serious loss of vacuum. Check all the lines too.