as kranzy said you shouldnt have any problems going to a ka24e as they're from the same car..
because you have to change the loom to go to the ka24e anyway, if you can find a u13 ka24de you should look at swapping to that. they have the same engine number sequence, so as far as the rta is concerned, its still a ka24e.. but to you, its another 20kw on top of the E