I'm sorry but being a bit provocative here, I just don't get it, Ive tuned cars myself in the past and its a case of diminishing returns for the money you spend. If you want more bhp and more importantly torque why not buy a Mog with a bigger engine in the first place it will probably be more reliable in the long term, and probably cheaper overall?
Unfortunately Morgan have a big hole in their product range. There is nothing between 154hp and 280hp. Not everyone wants the grunt of the 3.7 V6 in a trad chassis. Also in some countries the cost of tax and insurance is too high for the Roadster. Personally if I was going to have to pay that sort of cost of ownership I would want a much more sophisticated car. I like the idea of a Plus 8 but that is yet another step up in the cost of ownership.