First of all, no manufacturers introduce new parts in the spring. This is when the weather gets nice, everyone pulls their cars out, and the factories get slammed with orders. They usually are backordered on existing parts, nevermind new stuff.
Second, the industry trade show hosted by SEMA is always the first week of November. That is where everyone debuts their new stuff, because they know all the people in the industry will be there.
Third, don't expect any major developments right away. The 302 was brought out in the 1960's, and it wasn't until the 1990's that we finally got a huge selection of parts. Also, that engine was not as efficient in stock form, so changes had a bigger effect. One challenge the aftermarket is having is that they can't improve upon some parts from the factory, because the stock parts are already good.
Fourth, the design and tooling process for casting intakes and heads is incredibly expensive. That means only a few companies are capable of producing them. Unfortunately, the 4.6 is probably not on the top of their priority list. I hate to say it, but right now the sport compact market is the hottest thing going. They're probably working on heads for the Focus or the Civic.
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Moxie Racing
The Nitrous Oxide Information Site