The first intake is the same intake that comes on all 99-04 cars (updated in 01 with the metal crossover).
The second intake is the Dorman (junk)
The third intake will gain you some up top with the cost of power down low which is bad for a bolt on 2V.
The 4th intake is Chinese garbage
The 5th intake is the Dorman which is a NPI intake for all intents and purposes and crap.
The Trick flow is an attempt to copy the Bullitt intake and isn't really that great.
If you are a 99-04 stick with the stock (PI) intake. It is not restrictive and you will not see any benefit to switching intakes even with new heads. If you want to upgrade your intlet tract spend your money on a good plenum/tb combo (trick flow for $279 on Summit) and a cold air fenderwell intake.
2000 Mustang GT Steeda build #48. Bolt ons, suspension, Novi 2000.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.