Swap
id look into getting your block bored out and built. With that many miles i wouldnt start trying to put real power into it as is... even if you just tear it down and rebuild it as a 1.8 you will have a pretty solid platform to start building on... depends on your power goal and what you want to do with it. And dont forget that this is going to be pretty pricey. I am well into the teen$ with performance stuff alone and i do all the wrenching myself. My shortblock was built by Eurocode, and my head is still waiting on a build. Probably gettin done by 034 tho. But those are the only two things I had to pay labor on... If you get all this done at a shop, it will cost you some pretty crazy prices.
I think faster A4 for is wrong in saying a BAT 1.8 would be more reliable than an S4 swap. For one, you'd have to swap the 1.8, then throwing a BAT is always asking for hours spent chasing issues and wrenching. Now is it worth it? Most of the time! But is it more reliable than an S4 engine, making the same power? No.


