Brian, how many times have you removed the carb from the manifold? More than once then I would suggest you have an air leak via the paper gaskets that are on the bakelite spacers. If the car runs well when you put the towel on top, then I think you are getting the necessary air from under the carb base. I agree that if you are not gettring a solid stream when you activate the pump, than the tube is clogged or the daiphram is cracked. Cleaning the jets won't solve this problem as they are not in the accelerator circuit. When you remove the tube assembly for cleaning, be careful not to lose the 1/8" check ball at the bottom of the well. This may be stuck from varnish formation. If you need parts, let me know.