Practical experience with pump tuning - pure performance?

I have now read all the threads, but I haven't become much wiser from them.
Theory doesn't always provide clarity, so I'd like to ask all the tuning enthusiasts this question:
What practical experience do you have with pump tuning?

and on a personal matter:
I drive an A6 AEL with a 5-cylinder engine, 174 hp (chipped), and I would like to know what size fuel injection pump plunger is installed in my VP 37. Sure, I'd be happy to help you with that. Please provide the text you would like me to translate from German to English. I will do my best to provide an accurate and natural-sounding translation.
Hi Bastianna,