I have a 2012 GSR with 4k miles on it and the car started having issues and long story short after 26 days without the car the dealership figured it out. They replaced the Turbo and still had the issue replaced the clutch still had the issue, Changed all the sensors and still had the issue. Moral of the story is that the ignition coil went bad and that caused the problem..

My real question is now that I just drove the car if feels slow almost down on horsepower from before and torque, Is this a common feeling after replacing these parts and should it be like this?

This is a brand new car and all I had was a ETS intake and tons of parts in my garage waiting to go on. But now I am worried that the car cant even handle the bone stock settings and equipment then to mod it i feel like i will have problems down the line.

PS mods that I was planning to use were ETS 02 dump downpipe and a custom Exhaust replacing the cat as well as the intake and then a tune.

 

Your tuner will figure this out.

 

As far as what.... As far as I am aware my car should feel exactly the same as before it was replaced with all OEM parts.

 

I think he's saying that since you're planning to do a bunch of bolt-ons anyway, you may as well take all the parts to your tuner and work with him to figure out if there's an issue.