It all depends on the age, driving style, size of intercooler, piping to intercooler, exhaust, howmuch fuel at idle, max fuel at full rev..... I ran 18 s with no intercooler, modded LDA pin, extra fuel, no governor mod, and straight exhaust, and stock clutchwith intercooler, you will notice eaiser power potential, and cooler EGT, make sure the piping to the turbo and intercooler is fairly straight, and as short as possible. why not run a air to water intercooler?
so 2.5 inch intercooler piping, up the boost to say 20ish, eventually get a gilles pump, GTD injectors, add a bit more fuel...sounds good to me, i love mechanical engines
how's the low end? i'm thinking of a k24 on my 1.9td, but don't want to completely kill the low end power