New to the site and looking for some answers

I have a 2005 FPV F6 tornado ute 6 speed manual 138***ks
Recently been serviced all fluids filters oils and so forth.
Spark plugs replaced and coil packs as the car was misfiring which has defiantly sorted everything out the car is running smoother then it ever has before.

But......

Since the service I have had a loss in power, the normal kick from boost is very unnoticeable. I am getting the wind up of the turbo and flutter from the waste gate which tells me the turbo is still working but it feel as if I have the power of just a straight 6 . Also to that since spark plug and coil change I have lost quite a significant amount of exhaust sound, I am not sure if that is a sign of anything but where it had a nice big rumble it has now become quieter and sounds less aggressive,

has anyone experienced anything like this before ? Any help would be appreciated

sounds like you have not put back all of the turbo piping. there will be something between the hotside and he throttle body undone.
Also check the bolts on the turbo itself. The ones going to the manifold, they are notorious for working themselves loose.

You are dumping boost, not getting it to your engine.
This will also explain the exhaust noise, or lack there of.