It really bugs me when people go on about 'dont bother tuning the 8v engine, its a waste of money, dead money' blah blah fucking blah. End of the day, people may choose to mod the VTR engine because they dont want to be a sheep and follow the crowd and put a fucking S engine in!
IMO, logically speaking here -
A cammed VTR, with a VTS/XSi/S1/S2 gearbox will keep up with a standard VTS all day long. You also have to consider the VTR would be remaped to be able to produce the figure mentioned (117bhp)...you could have the rev limit raised slightly in the VTR from 6250 (or what ever it is) to 6500-6700 say (I dont think the internals of the engine would be greatly affected...but to be on the safe side, if you are tuning an 8v, you might as well upgrade the internals.
As for MPG - expect it to go down a fair bit...maybe even lower than a standard S...but its to be expected when tuning a car to maike it go faster - burning more fuel.
If you are tuning the 8v engine, you also have to consider the chassis set up on the car as well...if you have a decent chassis, I would expect the VTR to be faster round bends, and straightline speed faster as well...
Just my 2p anyway