New injectors? When?

[87homebuilttdi]

I have a BRM motor in a Jetta that has 139,000 miles on it, how do I judge when it is time to replace the injectors?
If I do, is it the nozzle or the whole pump-injector unit?
Is stock size the best for normal driving with a RC1 tune if looking for fuel mileage?
Who is a good source of these parts?

Also, has anyone had problems with crankcase blow-by enough to need an oil seperator, such as the MANN-HUMMEL Provent on the BRM?

 

[doug1976]

I changed mine because they were throwing an imbalance code and going into limp home. I wouldn't mess with them otherwise.

 

[Lightflyer1]

http://dbwllc.net/PDNozzleGuide.aspx

 

[MyAvocation]

My assumption is MPG decrease is one symptom.