Need pics of TTi setup

What is the deal with changing out the valvesprings? I see guys are doing that on their motors. Is it really necessary? How much would it cost to have it done?
the cat connects to the downpipe and before the -to cat back pipe
intake pressure (and more importantly exhaust pressure) will try to hold the valves open, to fight that you have to increase the spring pressure. stock springs can still survive around 6psi boost at normal rev's.





