Im running a 467.7/83/.90 I've never seen an s400 with a 73 or 74 exhaust. Truck is literally 100% stock aside from the turbo and H&S. Spoolup i slower but i would compair it to a stock turbo 7.3. Running at SPE tuning i would say the turbo picked up close to 100hp over stock charger. Despite what everyone says about the stock cp4 the truck has to be close to 600rwhp. It ran a 13.9 with a soft launch 1.9 60 foot, on 37"s and 6" lift, 3.31 gears and CCLB. That puts it at 520hp not counting for the tires and extra wind resistance. Also i hold 29k fuel pressure so i could add a little fuel.
I didnt launch any harder because i towed my other truck to the dragstrip with the 12'. Unhooked the trailer and raced. The turbo tows extremely well, clean and EGT won't go past 1120 degrees at full throttle towing 12k 0-80mph.