My friend bought a 97 A4 with 1.8T.

Available info:
034 motorsports Stage 3 turbo kit
Garrett T3/T4 57trim turbo
3"Stainless steel downpipe
3" exhaust with 12" vibrant resonator
Custom FMIC
Forge 004 BOV
Boostvalve MBC
Unitronics 440 Big turbo software
Delphi 440cc injectors
Innovate Wideband AFR gauge

I drove the car yesterday: nice power - FROM 4500 rpm on, NO drop all the way up.

NOTHING (literally, not even 5 psi) under 4000 rpm.

a) To be expected from 57 trim?
b) Assume .63 A/R (considering the behavior)
c) To get SOME low/mid power: change to smaller turbine. What is likly the current wheel? 57? 54?
d) If A/R is 0.63, how much will .48 help?

Looks like the stock FR is installed (I think 4 bar is stock).

Wideband showed no lower than 13. Assuming this is true: way to lean, or?

I noticed a 'pop' from the exhaust. Misfire? Friend says it happens quite a bit.

I appreciate your input/thoughts/suggestions how to give him some mid range power (even at the expense of top end power), and a 'save' setup.

Aside from driveability issue(some like it 'peaky'), I also noticed the turbo inlet
- has no filter or screen
- sits at best 6 inches above ground

Is that safe? It seems to me it is sucking dust, sand, snow, water mist (or worst case: pure water in a anything deeper than 4 inches) like Hoover on steroids.

I can't believe 034 Motorsport designed it this way.

What can be done to make it safe?