Hot start problems point to Fuel accumulator.
Regarding injectors -- For M103 its better to replace with new rather than get it flow tested because the price is so negligible. They are relatively easy to replace as well. Definitely a DIY.
Only way to test fuel accumulator is by either a) getting a shop to check fuel pressure at distributor or by getting yourself a CIS fuel pressure tester and doing it yourself. Somebody around here may have one you can borrow maybe? Check the tools section. You can always buy a generic one and go on ebay to get the CIS adapter. That is the cheapest way.
Here's the PDF on DIY
Check upper chamber (5.3 bar) + lower chamber (- 0.4bar below upper), and pressure after 30mins shutoff ( >= 2.8 bar). Pressure after shutoff will indicate accumulator problems.