Okay guys .Im new to audis. So I am having an issue with car going into limp mode. First ill tell what car i have and What mods.
2003 Audi A4 1.8t quattro with the tip trans.
big front mount intercooler
Aftermarket dv
Red top coils
Aftermarket exhaust
Boost gauge .

So issue is. With no codes on car at all i will run around for about a half hour and be hitting and holding 10 psi. Then I will hear a bunch of clicking right behind the light switch and then all the sudden im in what i assume to be limp mode .Car will only hit and hold 3 psi. Check codes and I will have a bank 1 lean code and a turbo underboost code .
Any ideas on why it does this? Does it need the stage 1 tune or is it something else?

Another issue is in morning with motor cold if I clear codes (same ones mentioned above) and then start car it will barely run and throw every misfire code it can.

I dont own a vagcom. Very new to audi. I am interested in getting vag com but i need more insight on where to get it from.
any help very appreciated and sorry for long post