You can get shims from C Sean Watts, search this site using his name or Hessian Imports.

The test outlined in blue was my experience. I felt that I got a decent (within 3 bar, actually ~20 psi) read on my injectors, but the slow test didn't work so well. Car runs nicely though, even though I was too conservative with my lapping on 2 of the injectors (leaks) and had to put 2 of the old ones back in. The #3 injector base and seat in the motor were a bit rusty, but had the carbon circle, the other injectors were a bit greasy. I think #3 was firing, but maybe weak? The prechamber looked the same as the others with a flashlight inspection. The motor smokes a bit less now, power is about the same, but I have to re-do the other 2 injectors for a final look. And I'll pop test the old injectors to see how they operated.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k

See Post #4
http://www.peachparts.com/shopforum/diesel-discussion/284501-complete-remanufactured-injectors-nozzles.html#post2541395

If the old Injectors are Bosch they are going to have those holes #14 and #15. The Idle amout of Fuel is supposed to go through those holes. So give the Handle on the Pop Tester some short strokes to simulate an Idle amount of Fue and to see if the Fuel goes through that central hole.
The Injectors on my Car had those holes plugged solidly with Carbon.

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84 300D, 82 Volvo 244Gl Diesel

I'm waiting on the delivery of a large face 1% 3000 psi gauge, dry, and mount that to see if i can be a bit more precise. Thanks for the heads up on the holes.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k

Go to a hydraulic shop and put a non return valve on the gauge, that way it will hold the peak pressure... just loosen the union to drop the gauge pressure back.

Doesn't mean much unless you IP is delivering the same amount of fuel per line, which is why a tester used graduated tubes and runs the pump at various rack openings and RPM.

Rule of thumb is service the pump every other injector service.

Personally I wouldn't dream of doing injectors myself, I can't compete with a professional on cost or repeatable and verifiable quality, because I don't have the very expensive professional test equipment.