ok..

1st.. do not bore the maf, do not CHANGE the maf.... unless your tuned for it. If you increase the ID size it WILL give wrong reading to the ecu.

So say the ecu thinks the MAF is 2.5", and you change it to 3.0"

The ecu calculates air flow by the voltage X by the maf size. The ecu will be reading 20% less air that is flowing into the engine, causing you to run leaner.

2nd.. that "screen" is a flow straightener (sp?) it adjusts the airflow so it can be properly read by the MAF. Stage 3 APRS come with a new/different one.

3rd. You CAN either buy a bored thottlebody, or bore out your current one (just buy one). This will increase airflow to the engine WITHOUT screwing up reading and causing a lean condition.

You could also get a P&P (port and polished) intake mani, exhaust mani, .. or get some headers.. get a more free flowing exhuast, or a bigger intake.

I hope that clarifies this more

 

That's why Mance ships his bored out throttle bodies with o-rings. The larger bore equates to slower velocity across the sensor. The o-ring creates a smaller hole which increases velocity. He's tested his products and I have too with an o2 sensor monitor (on my 97 12 valve).

 

you don't still have a link for those do you.

 

So more or less you have to test different sample tubes (o rings) to dial in the correct air fuel mix on the S3 maf?

 

pretty much, you can get a S3 MAF and velocity stack from mance, they are made to work together, i think im gettin that setup soon