there are some backyard mods that can be done, but some cost money, there is no need for magna injectors because there will be no big power difference on just bolt ons, it will have to push alot more power or be a boosted car.
Start with the basics.
Tune
2.5 exhaust / extractors
Cold air intake
v8 t/b
Diff gears 3.7-3.9s mini spool
take all the weight out of it spare tire jack all that crap all depends how bad you want it, you can go to more extremes like taking the deadner out ditching aircon there are alot of small things that can be done.
if he has abit of money get the heads shaved $100-$120 for both 30-40thou if you have a die grinder and bits and good with your hands port the heads,
a custom grind cam is about $200-$250 the list goes on. good luck there are alot of more things that i havnt said but if you do a search it will come up with tons of Qs and answers. but also at the end of the day its still a 6 and just with bolt ons isnt going to take on a gen III or something