A camping forum for VW bus and camper owners.
Wish I had the perfect answer for you situation. I would check your fuel pressure first at the metal T above the engine. I'm guessing you might have a restriction in your fuel lines, pump, or filter. The Bentley manual describes this process pretty well. Check it at idle and higher rpms. If this is OK then then next step is checking for air and spark.
Make sure your air filter is clean and that the air flow meter is moving smoothly and that it's "plugged in". The CO adjustment screw should be set by a mechanic with equipment. Mine is set for 4 full turns out counterclockwise. This is very subjective but may give you an idea as to where to set it.
Hope this starts you in some direction. Remember you need fuel, air, and spark to make the engine run.