thanks for the info! Peugeot confirmed the undertray is not standard/fitted on the 1.2vti... but I've yet to hear from them if I need one or not...regarding your inquiry, I also experience those things you observed/mentioned... I guess that's maybe the characteristics of a 3 cylinder vti...since its a relatively new type of engine, i think we just have to get used to it... I for one sometimes find my driving confidently and sometimes not...but I'm still convinced its a punchy great little engine and I'm looking forward to years of happy motoring....
BTW, I'm only getting 38-40mpg on city runs, clock so far is 1500miles...
cheers!