Any 1.8T engine management experts on the list?

[TM]

Hi listers,
Our A4 1.8T is having problems and I need
some help with the engine management system.

Problem is as follows:
The car exhibits a lot of lifter noise lately
(noticed it today during the test drive after
re-installing ECU) and makes a funny, sort of
wheezy, not exactly scraping, not exactly rattling
kind of sound under boost, but not very loud
either. Also, with the chip supposed to be
programmed at 1 bar of boost (gauge, not absolute),
I see only 12-13 psig on the analog boost gauge.

Putting the car under load in a high gear (e.g.
running in 4th gear at 2k rpm) results in boost
reaching 13psi and then wobbling back and forth
between 13-15 psi with a noticeable engine stumbling.
This appears to be engine knock with the consequent
retardation of ignition timing.

Why would the car do this and why would it be low
on boost? ECU was installed per instructions on
APR's website (although it is not an APR chip, the
ECU installation procedure is the same).

I am going to contact my vendor tomorrow, but am
curious to know what the cause of all of this might
be. Another bad chip? This is annoying.

Taka
'99.5 A4tqw