just wondering what you guys think, should i replace just the bad (#3) fuel injector or replace them all
..........i was thinking of replacing them all until i saw the price per injector

 

Depends on the milage I guess. If they are old, and in need of new orings, then I would do all them or upgrade to a bigger one and tune? Since you have to take them all out of the fuel rail to replace just one, then do them all? I guess it depends on your budget and how long you plan on keeping it.

 

A while back I came across a set of (4) JCW 380cc Siemens injectors at a salvage yard ($37). They looked really good so I tested, cleaned/flushed them with a homemade rig and ordered a refresh kit (thank you @JOHN21BLACK ),
from Mr Injector . The kit consist of 4) new screens and 8) O-rings ($28 shipped). Their search function is not easy to navigate; so it's best to just email them with your injector size/brand and paypal them direct.

There is a really good thread somewhere here on NAM about cleaning/refreshing and upgrading injectors...I just can't seem to find the one I was going to point you to...

 

I just recently went thru that eBay thing, just buy the real deal injectors and don’t buy cheap eBay $20 you don’t want that risk i took, if you need stock injectors i have single ones i can sell and send, Send me a pm

 

I will have to advocate for replacing all of the injectors - maybe the 380cc Bosch Audi TT injectors. Since the fuel rail is coming off anyway for that job, you may as well replace the fuel pressure regulator too and maybe the vacuum hose/pipe that serves it. This is from my perspective as the driver of a daily driven, 170k miles 2003 R53. Everything I haven't already replaced is probably due for replacement anyway.

I make my living fixing cars so I have no interest in tinkering with small repairs on my own cars. When I go into a repair in my car, I perhaps go overboard on the "while I am there" philosophy.