[Techno Duck]

Assuming you have a stock chip and a relatively unmodified engine, i don't think tuning is going to do you much good because you will just be masking an underlying problem. In other-words, you shouldn't have to do any tuning on Motronic fuel injection to get rid of lean running.

Motronic is very sensitive to vacuum leaks and these cars have many components that can introduce one.

I recommend you perform an evap smoke test... basically a machine that pumps a dense white smoke into your intake or exhaust at a very low pressure. This will help you find all of the leaks you have.

Intake manifold gaskets, to include the plastic spacers are common leak points. Also all of the vacuum hoses that are behind the intake for the brake booster and air / oil separator. Evap lines for the fuel tank also leak points. Finally check the j-boot and also the hoses for the idle stabilizer valve.

And BTW, Black Forest in Clairemont are a great place to talk to if you haven't already done so.