[s-cars] Boost problem HELP!

[JR]

I have a weird boost problem.  I have a 93 S4 with an MTM Stage 1 chip
(just got it).  When I first start the car it takes off like a bat out
of hell.  About 30 seconds later the power is gone.  It feels like the
turbo is barely working if at all.  I stop the car, turn it off (reboot
the computer?), and start it again.  Boost is back on and it pulls hard
again for another 30 seconds or so.  Then back to no boost mode.  Every
time I start or restart the car I have the boost again, but for less
than a minute.  I've replaced the bypass valve and visually inspected
the hoses without removing them (not that this does much good).  Does
anyone have any idea what is going on?  I'd appreciate it if someone
could point me in the right direction.

Thanks,

JR