This is my first venture into the air-cooled VW world although I have had along string of water-cooled VW's and Audi's as well as BMW motorcycles. With that out of the way here are my current issues. 
1 -- Found disintegrated EGR valve which will be replaced my question concerns the EGR Filter. How do check this component and/or what criteria do you use for replacement. This particular unit has been welded into the exhaust system which makes replacement a real problem.
2 -- Is there a way to check the heat exchangers to be sure that they are not leaking exhaust gasses into the heating system? This vehicle is missing the heater boxes as well as all of the flexible ducting and some of the connector boots giving rise to the thought that maybe there is a basic problem in the heater and no simple way to check it out. If the heat exchangers are bad I'd like to replace them while I have the engine out of the vehicle.
3 -- Where is the best place to source the heater duct and the boot from the booster fan to heater boxes?
Thanks in advanced for any direction/advice/insight
Gary Meier