Ok sr owners we have a issue!

Just had my turbo and manifold replaced and car sound awesome but we have another issue!

Car drives fine and pulls fine BUT when i hit 4k rpm a horrible metallic grinding noise comes it seems to be all gears but when I park and rev in neutral it is there but not as loud.

Before i had the mani and turbo done my gearbox when i hit 3k rpm the gearstick used to make a horrible vibration noise between 3-4k rpm now it doesnt and when changing gear there is a nocking from the rear (mainly second)

Not sure if they are link just seems sus that one has stopped and the other has started it makes me think its the gearbox well I hope because i dont want to replace the engine!

Any thoughts ?