Because you can get...
T-Stat at a local parts store: $10
AL104 spark plugs: $10
New Lifetime warranty wires: $30
Speed Daddy Headers from EBay: $220 shipped
3.4" ZZP MPS System: $100
Make your own intake: $50 or less if your good at shopping
Reptile DHP'd PCM: $50...and he is on here.
So...do some quick math...I got $470...so that is at LEAST $130 in your pocket...and way better performance because you'll be getting headers and and not a DP.