Problem is, I was sold an item that was supposedly it great condition and it is obviously not.
The intercooler manufacturer where I have had it tested does not recommend using sealant in the bolt holes due to the possibility that it will come off inside the cooler and enter the engine.
He has recommended drilling out the existing threads and welding in a new section of round bar which can be tapped properly.
To me this sounds like the best and most professional way to rectify the problem.
Back to my original question, There is no way an intercooler manufacturer would intentionally drill there mounting points through into the tank? I gather this is a correct statement.