Fuel in Coolant, Injector questions
 

I've learned alot reading this site but have even more questions
My Late '99 F-350 Bucket truck, 7.3, all stock, 107k miles, 10,000 lbs. has water in the coolant overflow bottle. The mechanic said it's the sleeves/cups that the injectors fit in. He has replaced 3 so far that were bad. Should he replace all of them? Is it better to remove the heads? We haven't done that yet.

The injectors are being tested. $32 each. He said new ones are very expensive so I am trying to find out if I would need new stock injectors or if I could find an alternative.
This is a work truck. I want the best mileage and reliability. What about rebuilt injectors? Who sells the best ones? How much are new stock injectors? Everyone seems to want more power from aftermarket injectors, but are there aftermarket injectors for mileage? What about matching the flow on a set of injectors like Diesel Systems Services (El Cajon, CA) claims to do? If they sell on e-by does that automatically make them bad?

As a newbie I don't understand all the code for the parts you all put on your trucks. Foil delete? Where can I find out about all this stuff?

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I'm reading about Swamps injectors. Nice guarantee. $1200 per set of 8. If I need to replace injectors, should I replace 'em all or just the bad ones?