On my last astra mk2 1.7d, i had a powerflow jobbie on it with single rear box only with twin 3.5" dtm's, and it was'nt quiet, anyone that heard it will tell you.
Think it was measured about 120db at CC action day(yes i took a diesel on the track) and yes they stuffed some lagging in the tail pipeslmao lmao
was great, a little burble from the tail when de celeratin, nice and deep on the throttle and for 150 squid wernt too dear either and i believe gave more mid range punch. mine was non turbo......then i found one on the manifold and did some back ground work on it.... it was done and i had 65.8 bhp and 89 ft lbs of torque and around 50 mpg (quite a bit lower cos u have to set the diesel pump up to run richer for the turbo when its on boost to fuel it properly)....basicly the same as a corsa t/d, it can be done on a n/a block mate trust me, i've done it and got a r/r print out to proove it. but it will only ever give standard grunt (i believe that the 1.7 isuzu lump gives 82 bhp with a turbo on it) in n/a trim they give around 64. worth askin around for mate, but expect to pay dear for the turbo 'if' u find one.
put it this way, when i first found out that u have to richen the mixture i went a bit ott and only managed 100 miles on a full tank but i did almost waste a honda crx thing (the 2 seater) away from a set of lights (over 100 meters he got 1 car lenghts in front of me) when we got to the next set he sat laughin at me....so i gave the gesture for him to wind down the window....then his face changed....... "that's a diesel" "fuc me" he said..."that dont go bad" i laughed at him sayin i bet i didn't use as much fuel as u did getin away from the lights lmao