[The Radium King]

full intake assembly from a 1999 3.4 and you can keep your cable throttle. may have some interference with the chassis due to intake height, but massaging and perhaps small spacers on the engine mount to lower the motor should set you up. can also get more clearance from a 987 engine cover.

since you have 3.4 heads already no need to drill/tap for the intake, but i think you'll need to run the 3.4 fuel rails as well (mounting is different) which will require tie-in to your existing fuel system.

think about maf and air filter as well, which will drive what you need for a tune. ditto injectors - later 996 runs larger units. a lots of threads here about 987 airbox, maf tube diameter, etc.

make sure your fabspeed headers are not for a 2.5, otherwise not doing yourself any favours.

you can boost these things, just don't get crazy unless you want to drop the compression. perhaps see what you think about your 3.8 once you fix the breathing issues before boosting. although 2.5 intake would actually be better in a boosted application ...