To make good reliable hp and torque you need a solid engine first.... Usually a weel built engine thats been balanced and machined properly will make good hp. Having all the block machine work is important. The carnk main bearing webs need to be machined straight. this is called line honing or align boring. Once thats done the deck of the block needs to be trued up so all the pistons are at the same height. All the rotating parts of the engine must be balanced. Porting the heads helps with the air flow in and out of the heads. That makes lots of hp. Then you need a turbo.... Any of the big three will work fine... Banks, ATS or Hypermax... Most use the wastegated turbo. Then the turbo back exhaust is necessary for flow... with a turbo we don't usually run a muffler because the turbo cuts up the noise signiture so well. Yes... The exhaust will sound loud but only when your really getting on ot like towing... then any engine sounds loud because its working... An intercooler is another way to add hp. This will cool down the aircharge going into the engine. Boosting higher than about 12 or 13 lbs is getting the air kinda hot. Thoughts are the air temp is passing 300 degrees at this boost. So its usually not done much.... some here are able to boost to 20 lbs and not suffer....
Hope this starts you in the right direction...
