If that's the case why are there so many tuning firms around offering double (or more) the horsepower on mainstream 'family cars'

Andy, not many (in fact, I can't think of one of the top of my head (although I'm sure there are)) do a full heart transplant on a vehicle.
I also - and again, I am not an expert - believe there would be a difference in liability between if the dealer sold a modified vehicle or changed a customers existing car at their request. To my mind, one is a sale of a new product (with all the liabilities associated) while the other is carrying out a customers request on their property.
I haven't driven the Mogvette, so I cannot comment on how it handles and performs but the concept doesn't appeal to me.
(ps - you mentioned "mainstream 'family cars'", don't forget these will have driving aids, passive safety devices and modern suspension and crash protection. Having owned an E60 M5 with over 500bhp, I can tell you the car never felt even close to the ragged edge (including at the VMAX on the autobahn). Would it be possible to say the same about a traditional Morgan with double (or more) the BHP of the Plus 8?)
