Tupac, I had a DTUK Tuning box fitted to my 54 reg Vectra 3.0 V6 CDTi SRi.
I was running the Harry map and then switched to the Sally map.
For about 6 months it was great. The difference between standard and the DTUK box was incredible. It really did feel like a huge performance boost.
However, about 6 months and two weeks in, the dreaded "Spanner" warning light appeared on the dash and the car went into limp home mode.
This happened a few times so I booked it into my local dealer to have a look at ( I took the tuning box off before it went in as the car was still under warranty ).
They diagnosed a faulty turbo pressure sensor and fitted a new one under warranty.
So I picked the car up, went home and refitted the DTUK box. Ran fine for about a week and then the spanner light appeared again. Stranded me in a car park in Perth. Got car taken to dealer again ( removed DTUK box once again before it got left there ) and this time they said the main engine management ECU needed replacing. Luckily this was also under warranty as it was about £600 worth of kit.
When I got the car back, I didn't refit the tuning box.
Thread related to this here :-
http://www.vectra-c.com/forum/showthread.php?t=33275&highlight=spanner
Sold it on a Vec owners forums.
It may have had nothing to do with the tuning box but I wasn't about to take the chance. So in short, I would be wary of using any form of tuning box, whether it be DTUK or otherwise.
Remaps would seem to be the better option from what I've read on a few forums regarding the difference between tuning boxes and those.