I use Millers
In my Brera 2.4 JTD I had a misfire / stutter running rough around 1500-2000 revs, any gear, hot or cold, rain or shine.
After searching the forums I tried Millers Diesel additive.
After a tankful of fuel mixed with a measure of Millers, the problem cured.
Went back to fuel only without Millers, problem came back.
Put Millers back in with next tank of fuel, problem gone.
I use this with every fill up now, keeps me smiling.
Also Just had a month ago a remap from AHM in Hampshire from 210 to 250 BHP. The difference is great. Smooth extra power no flat spots, better consumption. On a run @ 70mph I regularly get 41-43 mpg. Round town 35-39. Which is much better than before the remap. The power is available much earlier in the rev range, making a much more relaxed drive if you want and not changing gear so much if you don't fancy it. Top end is improved, acceleration is fantastic, about 0-60 in 6.4 sec. Midrange is a wonderful improvement.
I would urge anyone to do the remap on a 2.4 JTD. I only recommend AHM in Hartley Wintney, Hampshire.