backing off the aneroid (spelling?) on my 4630 sure fixed the low end power problem. starts and lugs much better now. I now just idle along with it when drilling seed, or running something small like a V-rake. and getting 2.5-3 gph while doing it.
And it's still running strong while powering a pto tub grinder with the injection pump turned up one turn... might be making near 200 hp.... sure been a good tractor for us.