I'm realizing the 2.6 is, shall we say, anemic.

Anemic is not quite fair. It is a 4 cylinder engine built to go in a truck. It has a reasonable amount of low end torque and can do pretty well higher up in the RPM band.

But, it is that. A truck engine. It is not meant to propel something at a great speed.

First off, what are you looking for? If you want to dust built v8's, sell what you have and get something else.

That said, there is plenty you can do to the 2.6. It is all listed here somewhere, it will take some searching for details.

Semi-Easy bolt on stuff:
-Header
-Cam
-Exhaust work
-Open style filter

A little more, but still bolt on:
-Bigger MAF from a later rig (I think you already have this)
-Larger single bore TB from a later rig (again, I think you already have this)

More intense in work and cashola
-smaller chamber head on an earlier block (sorry, you are already there.
-earlier pistons in a later block (a possibly for you)
-bore the block
-deck the head
-balance the recip assembly

All of the above will make it run nice. If you can bump the compression ratio (late head/early pistons) it really perks it up. Let it breath helps nicely too. Ignition stuff is a wash. The Isuzu system is more than adequate for whatever the 2.6 can throw at it.

Finally, regear. The 2.6 is happier spinning a little higher than what it does stock. Lower gears will probably make a grand difference. But, you will probably have to compensate with larger tires. I am turning 35's with 5.38's and am more than happy almost always. Big hills still bog it down, but it is better than it ever was.

Down side is you can't get 5.38's for your front axle anymore.

Good Luck,
Michael