free or super cheap I would start with some colder copper plugs like autolite 104's ,a 180* t stat , delete the u bend and resonator with straight pipe , make a homemade intake with 4" smooth intake tubing from zzp or intense , 2 feet will be more than enough and its about $10 a foot , put a cone filter on the end of it and use a roof flashing to keep the engine by heat out of the intake ( filter goes in fenderwell) you can heat wrap it with reflectix or cutup one of those reflective windshield interior protectors and hose clamp/wire tie it on.
"flip " the upper motor mounts - lube the rubber inserts real well prying with a flat blade to get wd 40 or similar in the area where rubber meets metal and use the same hardware that holds the "dogbones" to the mounts to index the rubber inserts 90* (1/4 turn) awesome free mod you will feel the response as soon as you move the car.
remove the engine lifting brackets before doing the plugs and save them , they will make plug access much better and if you ever need to remove the engine you could replace them but theres plenty of other stuff to hook onto , takes a couple pounds out , maybe 5 for free . remove the sc plastic cover , it just traps heat.
all this can run real low 14's add some weight removal or a tune and your flirting with 13.9's for a hundred and change.
next step would be headers and pulley (3.5) this should put it high 13's solid for $500 if you buy used parts , I ran 13.5 on less but race in a cold climate , at sea level and only on good DA nights lol.
if he wants 12's it will cost a lot more unless you go with a lot of weight removal and theres many paths there , intercooled , cammed , e85 , spray , etc...
a guy on the regal forum went 11.9 last year with $900 total including purchase of the car - lot of weight removal , used basic mods , and spray....
