As everyone knows, head flow is the major obstacle when it comes to 22R performance. In fact, the 22R head is the ONLY head I know of that flows better on the exhaust side than the intake side. Yet, when it comes to improvements, all that is available are various ported heads that fail to achieve much more than relatively incremental gains. What the 22R REALLY needs is a head with redesigned porting, like a Dart head for a SBC. Yet, nothing like this either exists or has ever existed. In fact, the only real option to this effect has been the 20R head. And that can’t accommodate fuel injection (something else the aftermarket COULD take care of, but never has). Why have there been no revised aftermarket heads for the 22R? Has it just not been considered a sufficiently popular motor to make it worthwhile for anyone to develop such a head?

 

The amount of effort and money required to make a new head just isn't worth it on a 40 year old design. If it was a good way to go, Toyota would have made a better flowing head or a DOHC version and not went with the 2/3RZ design that superseded it in the Tacoma. It's just a low reving tractor motor that's decently reliable.

 

Yes, and emissions standards were getting tighter and tighter, and Toyota had tweaked that engine all they could and were pretty much maxed out. They needed a new platform that delivered more power and ran cleaner.

 

It wasn’t a 40 year old design 40 years ago. But even back then, nobody made anything. At the same time, you can get better heads for all kinds of other motors. Edelbrock even started making a new head for the Jeep 4.0 a few years back. And that engine is pretty ancient as well.

 

I can only guess, since I never had friends who worked at any of the major players in the aftermarket suppliers back then. The biggest for 20R/22R would have been Downey offroad. But there many others. But these would be my guesses.
1) They couldn't come up with a design that made significant improvements over the oem design.
2) Cost. By the time they had a finished product it was priced out of the target market.
3) They couldn't get CARB/EPA certification to sell in some of the biggest states.(or couldn't afford the cert process)
I'm sure there are many other reasons that i didn't think of, but these should suffice for answering your post.

I saw plenty of customers have aftermarket stereo systems that were excited as all hell after the install. The improvement was that noticeable. I rarely saw a customer feel that way after new cams, headers, air intake, etc.
It got to the point where I wouldn't install them in our service dept. Partly because if it ever failed smog I didn't want to be dragged into it. But mostly because i didn't want to be associated with work that was most likely not going to deliver on all the promises made.