Wow. Have you checked the wrist pin and conrod dimensions, and checked that the skirt height will work with a different rod to stroke ratio than stock? I would be very, very surprised if Vitara pistons were a drop in replacement. Aftermarket D16 pistons are often pretty cheap, and I'd bet they're a lot better suited to a turbo setup than stock Suzuki non-turbo pistons. I've honestly never heard anything good about Suzuki engines that aren't on a bike.