From a diesel perspective, anything that isn't turbocharged is a waste of time from a tuning POV. Similarly, anything that isn't using electronically managed direct injection is a pointless tuning proposal.
Get rid of those two ointment bound flies and things get more interesting. My 2001 plated Peugeot 406 2.2HDi has been re-mapped from factory spec 136bhp (and it's pretty good in that tune with 235lbft to play with!) to a whopping 192bhp@4150rpm and 329lbft (yes, that's right, I have NOT confused Nm with lbft) delivered from 2250rpm. This endows the car with mid-range thump that wouldn't disgrace a Boxster or Audi TT with the silly enigne option. NO stopwatch necessary, this is a genuinely rapid car now.
All you anti-diesel folks will bang on about 0-60. Yep, well, I've never put a stopwatch on it in anger but you can do it in well under 8 seconds without going over 3500rpm! In gear is a bit of a giggle too - 50 to 70 in FOURTH in about 2.5 seconds!! 70 to 90 in fifth in under 6!!! Flat out, who cares, the factory spec is said to be good for 129mph.
Go figure for yourselves - and then dial in over 35mpg when driven in anger - at the age of 36 I've half grown up but, boy (or lady) do I lurrve that sheer muscle.
What you MUST do, however is;-
1. declare it to your insurers - although it's probably undetectable, any underwriter will do ANYTHING to avoid paying a claim
2. Keep your servicing right on the nail. By the book or more often with the oil/filter swaps. A re-map is really only using up the reserves the manfacturers built in to cope with neglect. Sometimes I wonder if it's done to make it possible to sell petrol models, though. I recently drove a BMW 328i petrol and it felt so bloody spineless in comparison.
3. Set aside a couple of hundred quid a year extra for tyres - you're gonna enjoy the drive
)
Kind Rgds,
Paul.