500SEC Fuel system problem

[hitwtom]

I'm having some problems with my newly aquired 1985 500SEC. It starts right up and will idle about 500-600 RPM, when I press on the accelerator everything seems fine until I get to about 1000-1100 RPM then the engine seems to choke and want to die (lack of fuel?). The car had been sitting for about 2 years so I drained the fuel tank, removed the fuel pump, filter, accumulator? pressure regulator? and tank screen. Cleaned everything and got a new filter, checked the fuel pump while I had it out and put it all back together. Still have the same problem. Also the throttle position unit? (circled in the picture) makes an awful lot of noise (clicking) when the key is turned on or when running. I'm new to the gasser world but I've got 2 MB diesels. Thanks in advance