Long story , but a few salient points for you,
1 You are swapping a car that is at least 10 years older and may have 10 years' worth of more problems behind it.
2 The +8 is a bigger and heavier car than the +4 Duratec, it does take more taming on the limit , you will lose that "checkable" handling.
3 The GEMS engine is as reliable as any of the other Rover V8 powered +8s , with a few tiny exceptions surrounding the combined fuelling and ignition system. If you chip it , you need to do both, AND you need to ensure that there is no back voltage through the ignition switch , as this will flatten the battery overnight , easily dealt with by someone who has experience of this problem (Mark Adams at Tornado systems) The engine was not well set up by MMC and lacks knock sensors, the chips are OK but replacing them brings a big improvement .
3A The GEMS system is classified as Euro 4 , so is compliant with most ULEZ regulations in UK.
4 You will gain a lovely soundtrack , that V8 rumble is hard to beat
5 Your mpg will fall dramatically from around 40 to less than 30
6 The power delivery is totally different , instant torque from low revs means very relaxed cruising, but the engine will not rev as quickly as the Duratec, it just "builds up" rather than screams , so you do lose some of that sports car feel (the engine was designed for a 2 tonne 4x4, so hardly surprising)
