And swap hood to get rid of the washer nozzles. Also probably the tail lights.

 

Did anyone mention the facelift doorhandles? What color is your car? If it's silver you can paint the rear valance for cheap (and easy).. maybe 15 dollars in supplies.

 

front bumper - i suggest classified from a part out
around 600+ from ecs. :0

i thought about this very hard but i figured a slow 2.8 a4 trying to pass off as an s4 would NOT make sense

 

as far as money, buy a wrecked or rolled b5 s4. buddy of mine picked one up for 1800. swapped everything in a 99 passat wagon. the hardest thing would be wireing in the harness. only if you got skillzzz. if not like the other members said sell your ride and buy a real s4.