You are correct with some caveat's.
This is not a North American version. it is a European version boxster
So no SAI system
What he is hooking into is the EVAP system.
At least that is what it appears to be.
The proper way to test engine intake vacuum is to disconnect the EVAP and SAI systems.
Then you test out the EVAP and SAI systems seperately.
So I am trying to have him run two tests one with EVAP system connected via the "TEE Fitting" and a second test with the EVAP system disconnected.
So depending on what the readings are and what the action of the gauge needle is (if any) and any differences from one test to the other(if any).
I will know what to have him test next.
If he has vacuum issues maybe I can point him in the right direction.
We should be able to isolate them to a system. SAI EVAP or Intake
If his vacuum tests are good then there are a few very simple tests he can do with the Duarametric that will tell me if his MAF sensor, potentometer, (gas pedal) and throttle position sensors are working correctly.
If all the above test out good then I would have him move to the fuel system.
Starting with a fuel pressure test at the fuel rail.
Simplest things first:
Go step by step from simplest to most complex
one system at a time.
The simplest system to start with considering his issue is the intake system.
The greatest amount of unmetered air from a vacuum leak is entering the system "at idle".
When you stomp on the gas as you say, the unmetered portion of the air entering the system becomes less and less a part of the whole.
So typically when you have an intake vacuum leak your idle is a little higher because it makes the fuel/air mixture lean and or the idle is lumpy or hunting.
When you give it gas the engine smooths out because the unmeterd air is becoming less and less a part of the entire amout of air entering the system.
If he was running super lean and creating detonation (as you suspect) he should be getting a flashing CEL and some DTC codes. misfire codes something He has none.
So I am trying to go with "my diagnostic procedure" to help him find the problem.
So
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