After seeing the stain of soot below my exhaust after the forced DPF regeneration the tuner did today I decided I would give the car a good long drive and try clean it out to see if there was any truth in what he was saying.
After work I drove 70miles out the motorway in 3rd gear at 120km/h so the car was reving at slightly above 4000rpm. I also turned on the heater and the back window heater to try get the car as hot as possible.
After driving for about half an hour in 3rd gear I turned around and said I'd drive my car home normally now and see if there's any change.
To my surprise there seemed to be a big difference in performance. The car seemed more responsive and there was a far stronger pull when I accelerated harder. Could not get over the difference!
There is still a bit of turbo lag which I was hoping the map would sort but considering how the car was driving immediately after the remap there is a vast difference. The forced DPF regeneration and my 70 mile drive today must of cleared alot of the soot.
As South_Bound also stated, driving in normally you would not really notice much of a difference but if you accelerate hard it definitely has far more of a pull and a kick off the turbo.
Considering completely removing the DPF now as my next mod as I'm shocked at the difference it made today
Its the DPF you need to heat up - not the inside of the car!
Any performance increase may be due to the DPF unblocking rather than a the remap
Remaps can be done specifically to increase bottom end power, on some diesels the bottom end power/ torque is restricted to help put less strain on the DMF (dual mass flywheel) mant remappers simply increase the fuelling so the remap "follows" the original map and the "low down restriction" is still in place - a better/ more expensive remap is more sophisticated and can increase bottom end but you may need to strengthen the transmission to cope with the extrabottom end torque
A tuning box often increases bottom end power/ torque more than a remap
A DPF delete can reduce turbo lag by allowing the turbine to spool up quicker - along with back box delete and decat can make a big difference , (as well as a free- flowing exhaust, as lenny has suggested)