No offense loudsho92, but the Magnaflow y-pipe you sell has ordinary 400 cpi ceramic catalyst, so it has no performance benefits over the stock cat unless the stock cat is plugged. Real high flow cats are few and far between. Expect to pay at least $200 ea. for good universal type high flow cats. If it costs less than that, they are poorly made junk or are not really high flow.
The Accel coil pack might deliver more spark energy, but they are poorly made, waste of money IMHO. If you are going to run a performance coil, go for the MSD instead. Even so, they won't help much unless you are running either high compression or forced induction, which makes it harder to produce as good a spark. Basically a high performance ignition doesn't really produce power, but it can prevent you from loosing power due to weak spark under hard conditions.
Doing ports is a good idea, I would go for that. Same for the UDP. The tuner however is gonna be the biggest bang for the buck, on a Duratec you could see as much as 30hp to the wheels. And it can optimize your other mods.
Best plugs are gonna be Autolite XP Iridium or NGK Iridium. Don't waste time or money on any other brands. An AFE air filter will help. I would steer clear of the K&N because they don't filter that well, they can contribute to MAF problems (which reduces performance) and they are overpriced. AFE doesn't have a drop in filter, but you could use a round cone filter if you make a proper cold air intake. Better mufflers are a good idea. I wouldn't mess with the stock cats unless you improve the engines airflow
I will be doing much of this stuff on my own ride, eventually, and I will be documenting any power gains that might result from it.