My tuner told me I max out my injectors at 6k rpm. What size of injector should I get to reach 400 whp safely by using the stock fuel rail?

My current setting was:

Vortech tuner kit
3.12 pulley
Utech
RC 440 stock rail
Kinetix ssv
Kinetix High flow cat
DC headers
injen ses dual exhaust

On the mustang 4wd dyno, it read only 329whp , my tuner told me their dyno read lower than other dyno!!??

Do you guys know how much WHP should I get with the set up I had

 

440cc should handle 400rwhp.....get a fuel return that would def help....if for some reason its still happens go 650cc to be safe on the injector cycle....

 

I am installing a similar set up without a fuel return and I am going with 600s

 

Just a guess...but I would guess that its your fuel preasure that is dropping off towards redline . The 440's should be plenty for the 329whp on a Mustang dyno . You would be making around 370whp on a DynoJet