Although some people have blown IB5 boxes, its usually due to massive power increases from turbo or supercharger. It is after all the same series as being used still in the ST150 Fiesta, though I wonder what Jamsport did to it on their 300bhp one......the gear gaps are a bit better on the MTX for the extra torque, but I've always found the change a bit slower due to the double syncro....not that one races or sprints.....

If you want to fit an MTX its quite straight forward, but unlike the engine just about every ancillary needs changing. Driveshafts, engine bearing bracket, gear lever and cables, clutch pipe/hose, etc..

Obviously the injectors give a bit less petrol than 2.0 ones but you can easily increase the power around 25% and still not max them out. Again swapping the PCM can be straight forward, but......apart from really knowing its taken from a 2.0, and uses the same number of Lambda sensors, (don't know if pre/post facelift is impt,so assume it is) you need 2 keys in case you later need to code another one without paying Ford (or a specialist). You carefully swap the transponders (might need surgery of the fob) for the PATS to your keys.

That's the easy bit........The Focus PCM security shield is the best one I've come across on a Ford. 16 gauge steel, break off head bolt. Your garage will hate you.

So for those reasons, as for one I'm helping a mate to do soon, I'd just leave it unless your planning on further tuning and lots of money