Even if the K/N showed zero hp gains it's worth it to have once since you don't have the recurring cost of replacing a paper filter...
You will notice a difference in how your car runs with it...I'd skip the wires and coil packs, the stock stuff works just fine
Really you want to get some 3.73 rear gears, the first mod any Stang should have
1995 Mustang GT Cnv 427 stroker
1996 Cobra with Kenne Bell 2.1 Supercharger dynoed at 12psi: makes 412whp/424wtq on E85: 250K miles on stock engine
2003 Infiniti M45 V8 340 hp
"What do you do besides drive fast?" "Have fun...."