figure this out---> DT407 injector pump

I had a '70 Farmall(International) 1456 tractor which had the factory DT407 engine and Roosa Master injection pump.  After the tractor would run for approx. 5-10 minutes and warmed up, it would begin to severly loose power, acceleration and RPMs, eventually just shutting down slowly on it's own.  My friend and I got a hair-brained idea(we were 13 at the time) to take the fuel enrichment screw off and we bored a hole(about 1/16"-3/32") all the way through the screw, then replacing it on the pump.  We ran a small diameter hose off of the head of the screw(which was turned all the way out, as it was before our modification) and up to the fuel tank to return any run-off.  This modification not only fixed the "dying" problem, but you could easily tell that a few more horses and Ft/Lbs were reaching the rubber lugs.  Can anyone offer some insight on the cause of the problem and the effect of our modifcation?  I can only speculate due to my limited knowledge of the pump itself...  
'04 F-250 SD PS Lariat AFE Stage I intake, 4" turbo-back
"not a real International Harvestor, but it's a start"

Sounds like it was a supply issue, or pulling in just enuf air to slowly kill it. You may have opened it up enuf to let it push the restriction thru, which isnt always good. It could've also send dirt into the pump when it broke free, but that's just my theory.  
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Daily driver: 67 F100, 300, 4V, 4 spd, soon to be 4BT.
My low buck fuel rate site:
www.freewebs.com/nevrenufhp/index.htm

cool, thanks for the insight  
'04 F-250 SD PS Lariat AFE Stage I intake, 4" turbo-back
"not a real International Harvestor, but it's a start"