Injectors

The fabric covered hoses between the injectors is called " bleed-off hose" as is available from dealer $$ and on line. It's rubber dries out from the engine's heat, cracks and leaks. Buy 3' of hose, get a utility knife and pliers, cut off the old hoses near their attachments (so you get the length right for the replacements) and cut the residual from the barbed attachment on each injector. Use the pliers to push the new hose onto the injectors. The #4 cylinder has a very short hose attached; it contains a small steel plug. Also replace this hose but insert the steel plug into the short hose before attaching the hose to the injector.

Wear gloves, the fuel stinks!

This is absolutely what you should do first. But if your mileage still stinks after doing this, you -might- have cracks in your injectors, and would need to rebuild them. To take them off, you'd need a 27mm socket (that costs a fortune) and you could take them to most heavy truck repair shops - they have ultrasonic baths that can detect even hairline cracks, and then rebuild them appropriately.

A 27mm deep socket should not cost you a fortune. I've even seen them in Sears for under $9. I've never heard of hairline cracks in Bosch injector bodies but I own the older 3 liter five cylinder diesels. Perhaps it's a problem with the newer diesels? You can also get Bosch rebuilt injectors and they are not too expensive.