1. gut the airbox and either run a tube down somewhere with a open element filter..or just stick on in place of the airbox...secure it as nec.

2.180 deg therm...no lower enless serious mods and tuning where done first.

3move the IAT sensor as far away from the engine as possible...itll read cooler air temp...wount be as noticable until higher speeds b/c air is movin faster...free mod...noticable improvments.

4. ecm programming or chip..id go with a tuner program...cheaper and you might learn something.

5. dont buy expenive plugs...stick with the recommended ones...

6. gut the maf sensor (if these have them)

7. if it has a TPS drill out the mounting holes to make it adjustable. check manuf spec for the volt reading initially to get a base, then advance it little by little...youd be surprised at the results (im a v8 guy, we have a tps, most cars do, but not sure if the 2.7 does)

8. if you want to get creative..ive seen +30hp on a stock denali fitted with a h20 or h20+methanol/ethanol/acetone/widsheild washer fluid injection system...do a google, youll find tons of info. after that...increase yer plug gaps and tps again..reset ecm...and go like hell.

9. speed limiters and transmission lock-up (1:1 ratio of trans output to front wheels...i.e overdrive) can be easily (it was on my 700r4 AT) modified or made switchable through the vehicle speed sensor on tranny or transaxle or whereever it is...look at service manual and get creative.

like is said...im a truck guy, but all engines are very similar...did these to a 99 silverado..same type of ecm system (OBD2) and the results were well worth the garage time and tuning time used.

ok..now im a truck guy...got a ground up built chevy 1500 with a 450 hp 350 lift tires ect ect...my wife has a nice little sebring convertible limited with 2.7.  im to tired of workin on my rig  so im lookin at her 'bring.  on this topic of thermostats i have alot of advice...and im sure most of it applies to the car as well.

recommended by most v8 guys...180 is optimal with minor engine mods like intake and exhaust...but i had one on my bone stock 350 with great results.  i had 'a overheat problem with the brand new engine so i put on a 160..stayed cool..BUT..and this turned out to be a HUGE BUT...THE DANG THING NEVER GOT OUT OF "WARM UP MODE"  it was getting chocked to death..mpg fell...performance dropped...threw codes...all in all...bad. 

160 deg therm is for mid to extreme ecm tuned cars...forced induction and major mods like that. 

my opinion...dont go lower than 180...but DO GO TO 180 when you get a chance..$$$ well spent.  regardless if its carbed...OBD1 (like mine) or OBD2

anyone please correct me if my assumption that V8 logic is the same as v6 logic.