I just came up with a solution to the problem of generating multiple IMEI code on mobile phones which based on observation is lacking.
You can now easily in 2016 generate as many as you want with this wonderful android app "IMEI Generator".

Features of the App
1. Now you decide how many IMEI you want to generate which of course will
all be valid.
2. All of the generated IMEI will comprise of 15 digits.
3. Your base IMEI is not necessarily 8 digits. It can be any digit less than 14 digits.
4. All the generated IMEI will start with the base IMEI.
5. The file containing the generated IMEI will not replace existing ones

How to use IMEI Generator:
1. Enter the base IMEI (max. of 14 digits).
ex : if you have IMEI like "35467698xxxxxxx"; you can type the first 8 digits "35467698".
2. Enter the number of IMEI you want and click generate button.
3. After this you will see the path to the file of the generated IMEI below the Generate button.

You can download the app from https://www.dropbox.com/s/xa2l4umozw1gljt/Imei%20Generator_1.0.apk?dl=0

Enjoy the app and share with others.