Time for custom tunes. He will never want to go back.. Might just want to go forward though!!!
I think I've swayed him as far as custom tunes go. He'll get a serious case of the perma-grins once he experiences them. In my experience, there's nothing quite so good as live tunes. The tuner can get it like
you want it in every tune.
Other than tuning and injectors, he'll be adding supporting mods like Swamps IDM, bellowed uppies, new boots, aftermarket HPOP (depends on what's available ?), maybe the ccv mod and a RR fuel system. Should be a very nice running/looking set up that he will be happy with.