I saw http://www.thingiverse.com/whpthomas/designs design of upgrade extuder head, and since I had problems with this, I made a derived a new design that fitted my Replicator 1 Dual.
Using a spring that we have at work its partNo 1180 and should be avalible as a spare part for Poseidon diving equipment.

It is also made for the dual extruder thats why it is sticking out upwards instead of on the sides, and the adjustment screw is inside the handle.

I made the pressure of the spring adjustable so that it would be easier to get the best result out of the print, and I have printed for 980 h without any feed failures since I made the upgrade.

I got the original solidwork files of the whole Replicator from
http://www.thingiverse.com/tlalexander/designs
Which made the design work easier.

I got myself another printer, Replicator 2x, got it cheap because the previus owner had problems with it.
So I made a new base that will fit the 2X, with attachment for filament hoses, the other parts is the same.

You can follow the instructions of whpthomas, will work for this version also.

I printed the new part with
Standard mode
0,1 mm
4 shells
99 % infill