I put off adding my intercooler (6.0) for several years because I was worried that my non gated turbo would have more lag.
The boost gauge does show a little more lag than before, but if you didnt look at the boost gauge you would swear it improved turbo spool time.
Dont worry about the numbers, it will add power to your truck.
Pulling a load, in OD and 2100 or so I run 5-6psi and 800-900deg. Wot with same load, speed and rpm, I get 10psi and 1100 deg.
What non gated turbo do you have???