When you are thinking about engine options also factor in 'The transmission' as part of the package.

In SA, with the basic engine (2.3L 5 cylinder) comes with the four speed.  ALL other engine options come with the close ratio .457 five speed.  The five speed makes better use of the engines power, while giving you a overdrive.

If you are thinking about spending bucks to go to Tii conversion I4, you will spend @$5000+ for the engine + ??? for labor.  Add a close ratio tranny to make up for the lacking low end, add another @$2000 on top of what you have spent and you would pay for a WBX rebuild w/mods, SA 5 speed, hoses, and many other parts towards a restoration (Which I did).

You can modify an engine AND ADD a .457 SA five speed tranny for about the same cost as the Tii conversion alone.

I just put on a new ECU (I want to run the new ECU before I add the Upgrade chip, to get a before and after conversion performance).  With the new ecu the top end power is a stronger, bottom end is smoother and the gas mileage has increased about 1 mpg around town (I have not tested at highway speeds, 65-75 yet, so I should also see an increase on highway mileage).

Like I have said, I can go in fifth from 40mph (35 if I do not feel like shifting) to 90 mph+.
Fourth can go from 25mph to 75mph.
The engine can go down to 1500 move the van with no trouble.  I can keep it in fifth

Adding the ECU chip upgrade will increase both power and mileage.

While you can swap to the Tiico 's kit, you would then need to spend more money to make it run better at low end: cam, intake and other changes to make better power at low speeds OR live with having to rev the engine, which can then shorten it life....

Robert