1600 DP Running 34pict 3
What size jets should I have?

Hi

From memory, 125-130 main, 60z air corrector & 55 idle.

Steve

checked jets
have 150 130 & 55

Would this explain my poor mileage?

The standard jets are main: 127.5; air: g55. According to Bentley manual. You can go bigger on the main for more performance, but maybe try 130 or 132.5 first. [We have a higher comp. 1640 with a few tricks to it (but still running standard 34 PICT-4) and it likes 135 main and g60 idle. Itwants more, but it drinks too much so it's stuck with that for now.]
If your main is 150 it sounds way too big, unless the engine is modified. Not sure in that case what the 130 would be?

The various parts that I can see in our standard 1600's carb (34 PICT-4) are:
Venturi: 26, Main: 127.5, Air corr.(looks like emulsion tube): 60Z (manual says 75Z), idle/pilot: g55, pilot jet air bleed: 47.5 (manual says 147.5), float needle valve: 1.5.
...I've pulled them apart many time sbut have never managed to find the several other items mentioned in the manual! You shouldn't need to change the idle jet. Your local VW specialist might swap the odd jet for you, or sell spares.