Function
To measure boost levels.

Part numbers
• 403A028 A'PEXi EL series mechanical boost gauge

Comments
I purchased an A'PEXi EL series mechanical boost gauge from Options Auto Salon in CA. I thought the gauge would make a good companion to my upcoming chip install since it will allow me to keep an eye on the boost levels in stock and chipped modes. Armed with information on the output of the turbo, I should be able to spot turbo-related problems early.
Initially I asked my chip dealer if they could install a gauge at the same as the chip, but they said they're only in the chip business. This forced me to do some research into the various gauges available and who installs what. After reading through numerous installation stories posted by other Audi enthusiasts, I worked up the courage to buy the Apex and do my own boost gauge installation.
By comparing my measured boost levels with those reported by other Audi drivers, I verified that I did the install correctly. It was interesting to learn that the manifold is in a vacuum state (lack of boost) most of the time. I measured boost only when accelerating aggressively during passing maneuvers and quick starts. Even then, I was only measuring 4-5 PSI. I managed to get the full 7-8 PSI of boost only when flooring it. In other words, it is quite possible to drive around all day in a purely vacuum state!