Spencer Zwiefel

So im in the middle of a motor swap, I had a BGN 3.0 in my Audi a4 Quattro that i'm thinking had a crack somewhere in the block because it kept using coolant and a new head gasket didnt fix it. So I ordered a motor off ebay with 79k miles, but when it came I was in the middle of pulling out the motor so I didn't get to look closely at it till 3 weeks later when I pulled the valve covers to start to replace the timing belt. Welp, much to my dismay I found a ton of rust on all the cam lobs, so I gave the guy a call and he came and picked it back up a few days later and gave me a refund. So I ordered another motor off Automotix, that one came a week later, and I checked right away this time for rust, but thankfully I found no rust this time, and everything seemed to be mint. Anyways, getting to the point here, today I was working on replacing the wiring harness and I notice the engine tag is AVK, and the one that was originally in the car was a BGN engine. What's the difference between the engines? Will I have to replace the ECU or anything like that?
Thanks, much appreciated!