welcome
I had a couple MKIV's 1.8T's
your mods sound pretty close to my 2002 GTi (traded her in on my GTO in Junction City, Or)
have you tracked your milage yet?
I was getting about 28-29 on open highway (70-75) with my GTi
and 32-33 if I could keep it closer to 60mph
does your Wolfie have the stick or the Tip(tronic)?
you said stock wheels,
have you considered Disk (wheel covers) on Steelies?
MOON Disc Snap-on Type
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2005 GTO 6.0 V8 (600hp)

1991 Geo Metro 1.0 3/5 base

2010 Prius II (replaced 2001 Tahoe 5.3 V8 April 2014)

1994 F-350 7.3 TurboDiesel (Rollin' Coal)