I think that Jez's dyno reads lower than many others, whether his is more accurate and others inflated, who knows ? You cant compare one dyno to another that's for sure
My 370z made 299 on his dyno with K&N drop ins, post maf tubes and an invidia cat back , and only made another 10hp once uprev'ed.
What the sheet says doesnt matter one little bit , its how it drives , you simply cant expect big gains on a n/a car so dont go with big expectations
Your car will drive a great deal better once Jez has played with it for sure !