Iam planning to upgrade my fuel injectors to 555cc. I want to know what is the
limit of stock turbos with an upgraded injectors? ECU upgrade? I want to hit 450+rwhp with stock turbos. Thanks!

 

I don't think that you would see much gain by upgrading your injectors on stock turbos. Injectors are usually done in conjunction with a turbo upgrade to keep up with the added air flow. You could get the sport500s, which are relatively cheap, have stock like spool and flow about 25% more air.

 

450 RWHP on stock turbos ain't gonna happen. If it does, it'll be very short lived; meaning that you'll wind up finding the turbine shaft somewhere in the midpipe. 400 is pushing it.