I saw one of these only yesterday and they still look fantastic in an 80's kind of way. It reminds me of a cross between a DeLorean DMC-12 and a VW Scirocco - that is supposed to be a complement by the way.
The turbo on the Isuzu engine physically works the same as on any other. It needs both RPM and throttle opening to generate boost.
I just wanted to comment on the "cross between a Delorean and a scirocco". That is a very good eye. These three cars were all designed together (along with the BMW M1) by the same italian designer. I am on my third Piazza now. I love them. Maybe I can keep everyone from running into this one.
When I was growing up as a kid, just next to my house was a dealership that only sold Isuzu Piazza Turbo's. I used to walk past them every day on the way to school and though they were the most beautiful car on the road. I loved the Turbo signs they had, I used to think they must be soo fast.
I guess that's why I also loved the VW Scirocco, as its been pointed out they were by the same designer. If I am ever rich enough to have more than one car then I would definitely get a Isuzu Piazza and a Scirocco - oh and a Lotus Elite turbo. Oh the memories of the 80's.
Just bought a piazza turbo for 200 quid. Wicked car goes like stink. Not as refined as my xr4i though, but still 200 quid bargain!!