I would not go to the bother of fitting a full decat, exhaust, restrictor ring, plugs, fuel pump, fcd, filter element, and boost gauge to then not take it to a rolling road/hub dyno.
In my opinion there's no way you should assume the fuelling will be fine when running at 1.2bar. For peace of mind you an fit the Walbro but that should be no substitute for a full check on the fuelling. You may find yourself running a little lean in the higher revs if you're boosting 1.2 bar to the redline. The stock 440 injectors are capable of fuelling this but you may need a piggyback to do so. (Emanage, SAFC II). The 440's should see you up to about 380hp at the hubs on the Thor dyno but not a great deal more.
Hope that's of some use...
Dan