I'm going to increase power in my turbo, the target is 550-600bhp but the car should be still good for everyday use. I have some proposal from 9ff, Techart, Gemballa, Sportec nad Ruf but I really don't know which is the best from them. Also I'd like to change exhaust but the best solution for me is rather silent to 4k-4,5k rpm and noticeble louder to the redline.

Please give me some advices, thanks in advance.

 

You will only need a chip and exhaust with the X50, so I´d recommend you call RS Tuning. They are one of the best in the business.

RS Tuning

 

I say call Imagine Auto....I also have an X50 and all I did was ECU remap and exhaust with 100 cell race cats and I got just under 500rwhp last time I dynoed....
European tuners are generally pricier than US ones and sometimes for no reason!! IMO of course...

 

Forgot to add, definitley change your dump valves to Baileys or something if you plan on running higher boost as the stock ones WILL fail over time...