APEXi and other boost controllers

[auditude at neta.com]

Hello,

I've been driving my '88 5kcstq fairly regularly now.  I'm enjoying the 
car.  Since nothing has broken yet, I was thinking of chipping it 
soon.  Fuel consumption really seems to suck tho'.  Between the 
full mark and the first part of the red on the gauge, I'm getting like 
250 miles.  I haven't done the math with the receipts I have to see 
what actual mileage is.

By the way, yesterday the check engine light flashed momentarily 
while accelerating around 4 separate times.  No other symptoms 
were apparent, and I haven't pulled the codes yet.

But, the purpose of this post is to ask about those aftermarket 
boost controllers that companies like HKS, APEXi, and Blitz sell.  I 
have a friend with a 2001 A4 1.8tq, and he's got one of those 
APEXi ones.

What exactly do those controllers do, and do they help on a 
chipped/WG springed car?

I thought the digital rendering of an analog tach was pretty cool, as 
well as apparently being able to select the boost at specific rpms.  
It may have had a turbo timer as well.

Thanks,

Ken Keith
'88 5kcstq
'85 4ksq
'94 SL2