How realistic it really is?

So few days ago I tried to recreate an engine from mazda b2600 pickup truck (gas, 2.6l, I4...). It seemed easy because it's a simple little reliable mazda engine. I have found all of the info of the engine after maybe 2 hrs of searching everywhere while building it in progress. At the end everything was looking fine and just makes sense... I hope... it should have 😝. But the engine was having a couple of issues like with firing, knock, compression, etc. I made it better by configuring some simple stuff and increasing the quality to the top which don't make too much sense, I mean it is a Mazda but man, even they don't have such quality 😂. Engine worked in the end but was too underpowered. And before you ask, yes, I have found everything from simple materials of the engine to all valve details and configs... Still, I love the game and it's really nice, you can't make such stuff 100% perfect, but what do you think?

Also idk what flair to give this, it's just a discussion and not really about the replica 😅.