I popped into Stealth after the Glastonbury festival - we had driven from Dublin/Holyhead down to Somerset via a night's camping in the Brecon Beacons, and drove up to Leamington Spa after the festival - so was well placed to judge the before and after. Unfortunately I was a bit zonked when I dropped the car in, and have misplaced my printouts, but I think I'm now running 106bhp on my 75bhp TDi. Aside from the car stinking of cider (leaving your car parked up a weekend with 5 litres of Wilkins farmhouse scrumpy in the boot - ongoing fermentation, plastic containers, time and heat don't mix well), the car is much more willing to accelerate through all gears, pulls away more strongly from traffic lights, and no downsides (smoke, fuel economy, etc) evident. I'd been caught by a nice policeman with a speed gun on the way down through Wales, so I wasn't going to risk a second brush with the law on the way back to the ferry, but it feels like it has that much more poke now - motorway overtaking is noticeably improved.
All in all - I'm a happy camper with Stealth. Had cruise control already. Just need to improve the tired stock suspension now ( or when there's some money in the kitty).