Is the ECU(under hood on passenger side fender) the same for 96 and 98? My truck is acting all kinds of stupid and I'm thinking of swapping in a '96 ECU into my '98.

 

Yes, same same.

 

Got to have matching numbers or it won't work.

 

What numbers?

 

The numbers on the labels on the ECUs. If they don't match it won't start

 

Don't waste your time trying to figure out if it can be switched, it can's, every year was different.
So, that being said what exactly is the truck doing wrong, and be specific, what have you checked so far and what codes are you getting?

 

I'll just start a new thread, too much story.

 

You own these two trucks right?
So swap the ECU's and see what happens, worse case you swap them back right?

 

Spike, by now I would think that you are aware that you can not swap an ECU unless you also swap the BCU from the same donor vehicle.
And yes they ecu's are programmed differently by Rover to meet new upgrades to the engine as well as emission standards.

As for the need to start a new thread, yes, you can do that or just realize you were given bad information and I just happened to find it so you don't waste too much time making your truck right.
Still hope you answer the questions I asked so maybe we can help you, that is why you started this thread, isn't it? May find the problems have nothing to do with the ECU.

 

He did, they didn't work.

Swap both the security ecu and the engine management ecu and it should work.

Edit: nevermind forgot about advance evap..