93 300D disel mileage loss after repair

[axm1955]

Hello all,

Am quite at a loss over the issue: Avalve almost directly under the injection pump. The valve has 4 3/8" connection onto it, one (the front one) going to the fuel filter assembly, two middle to the firewall (I assume to the tank) the forth to a side pipe also going to the rear of the vehicle.
This infamous valve begun lealink about two weeks ago, I removed it capped the hoses went to my dealer and purchased the restore kit (one O-ring and a washer) they called it a "monovalve". The kit resolved my leak.
Now the question:
My mileage went from around 31-32 on highway to 22-24.......checked all around the unit to see if I had disconnected any hoses or damaged any other items in the process, but was unable to see any thing damaged.

What could I have possibly done by repairing this valve to make this drastic change in my fuel milage?

Any hints/suggestions are greatly apreciated.

Adriano