Note: Buying a KLZE curve neck will give you the KL01 (DE) cams but will still have the higher 10.0:1 compression ratio, while buying the straight neck KLZE will include the more aggressive KL31 cams. 

Making sure you're getting what you're paying for:

Upon choosing your KLZE pay close attention to the following because it's very possible that you will deal with less than reputable JDM engine shops who will try and sell you a ZE/DE Hybrid without you knowing it. At the very least, perform a compression test. There should be at LEAST 200 psi in each cylinder. Some people have noted that the compression on a ZE engine should hover around 220 psi on all cylinders. Also, pay attention to the heads as they should have KL31-1A1 and KL31-101 stamped onto them. Also, remove the valve cover and inspect the cams. You should see KL31 stamped on them. There is also removing the spark plugs. Shine a light down in the hole and you should see flat-top pistons. Personally if I were missing any of these things on my engine I wouldn't buy it.

ECU:
With OBD-1 (93-95) it is better to use the J-Spec ECU and VAF. You can however run your stock ECU/VAF, although it won't properly manage the VRIS points. An explanation of VRIS can be found here:
http://www.mx6.com/forums/2g-faq-gen...know-more.html (FAQ: WHAT IS VRIS? (everything you wanted to know and more))
In this case you will be looking for the KL31 or the KL36 ECU. In the case you have an automatic, only the the KL36 will work for you, and if you have a 5 speed manual, either ECU (KL31 or KL36) will do fine. In the case of OBD-2 (96-97) You either have the option to Swap your harness to OBD-1 and get the above mentioned ECU, or simply leave your stock ECU in there and don't bother with it. 

VAF (MAF) Sensor: 
It is recommended to utilize the VAF designed for for the KLZE. This is the JE50 VAF and is found stock in the 1.8L V6 engine of the precidia (MX-3) and not compatible with OBD-2.

With the ECU and VAF you will fully utilize the performace offered by the KLZE engine, but keep in mind that these two things aren't compatible with OBD-2. Even if you can fit the JE50 VAF in your OBD -2 car, you will have idle problems and you will burn rich. In retrospect, the KL31 and KL36 ECU isn't recommended for a KLDE engine, there are no HP gains using this ECU on KLDE engines. 

If you are driving an OBD-2 car, and you swap the DE's intake manifold for the ZE's manifold you will get a check engine light cause the ECU is looking for the EGR system. In contrast, this problem doesn't exist with an OBD-1 car equipped with the KL31 or KL36 ECUs as the ECU doesn't recognize an EGR system, therefore doesn't look for it. With OBD-2 you can simply keep your stock DE manifold but you will lose a bit in terms of performance