i spent most of the afternoon there - not to have anything done to my car, just to have a chat with the guys at mango's and drive some of their modified cars. i can only echo what james has said - the upgrades are superb. i drove the following:
159 lusso 1.9jtdm
147 ducati corse 1.9jtdm
brera 2.4jtdm
brera s v6
all had been given john's (the master technician) magic treatment - the 1.9 diesels running at 200-205bhp, the brera diesel around 250bhp, and the brera s with maybe only a couple of extra bhp on the standard 260 but with the induction mod.
the 159 felt very strong - a massive improvement on the stock 150bhp. then i tried the ducati corse (standard is 170bhp, mango's one running at 205bhp ) - WOW

john has done an incredible job on it. it was seriously quick, but the thing that amazed me most was the sound - john has engineered the induction to sound better and my god he's done a good job, it really did sound like a petrol once you press on. i was genuinely surprised at how good it was
then came the 2.4 brera, again very impressive - massive torque and a great rev range for a diesel, along with a nice growl. quite a 'grown up' car - quite relaxed in its demeanour considering it packs as much power as a GTA and over 400 lb ft of torque
last of all i drove fraser's brera s v6 with the modified induction - pretty damn quick as you'd expect, and not overly loud under normal load - but over 6000rpm all hell breaks loose

it's been engineered to start really singing at the top of the rev range - and that noise could be seriously addictive, it's just brilliant
julian from mango's was saying that pretty much everybody who's tested the modified cars wasn't leaving until they'd taken the plunge and had theirs done. they really are a very impressive range of cars, i can honestly say mango's have done a great job.
they also layed on a nice spread of sandwiches & nibbles, and ian simpson's black 8C in the showroom was a nice bonus
anyway, like the others have said - if you get the chance to go there tomorrow it's well worth it
i'll be doing a piccie thread soon, i'll stick the link in here when i'm done