with the Borla Exhaust, and plus my K&N Cone filter, I see a diff in Performance, more on high speed than off the line.I got just the Mufflers done and got new tips, it Sounds Awsome! got a very low rumble Sound and when you step on it, it really goes good! Iit was recommended to leave my stock 2.1/4 Pipes by my Performance shop.Also my Gas Milage has gotten alot better! and with my Springs, the Ride comfort is still there, a little stiffer around corners.. I love it. Overall I am happy with everything on my STS! Can't wait to drive again..(@ work right now)
I paid about $650 CAD here in Vancouver B.C. which is not too bad.. as for Shocks and struts, I asked my Performance shop and they said I don't really need it as I am not going too low and so I didn't need to plus the car seems to like the Springs . I did a full 4 Wheel alighnment, and they had to adjust my Toe in or out (forgot) and everything came out great! Always get a alignment done after changing the tires or springs, Its a must or you'll eat out your tires! Take care! GO Canucks!