Question: Requirements for safe limit 300hp 1.8vt

[DeathLotus]

Hello, I had a few things I wanted to ask and couldn't get a based answer on Google. First things first, I own an Audi TT '00 1.8vt [180 stock], now 225hp stage1 (AJQ) about 330.000km. so I was wondering if I changed to forged (pistons,rods,crankshaft) and replaced to ko3s to a ko4, would I be able to see a safe limit 350hp? if not what should I expect. what mods would I need to have a reliable 300-350hp daily car and retain as much fuel efficiency as possible? Would I need to change anything else? such as valves, lifters or even the entire head? I'm quite happy with the current powerband but I'd love a little bit more for the straights, power is great through the curves, never had to flat out (mainly cause it's fwd and it would understeer but that's not the topic). Any idea on where should I search for 1.8vt forged parts? Cause I'd be happy af if I only had to change pistons,rods and a crankshaft to get a safe 300 as I've seen people do 500 on stock internals which surprised the living *#*#*#*# out of me. sure it could've been a BAM or a similar code but still, if it can do 500 and run, then it should do 300 safe right..? I mean I'm just using common sense here.. Thanks a lot, I'd love your feedback on this!
The link below isn't mine but I'm not deleting it out of curiosity.

- Read more at: https://www.torquecars.com/audi/18t-tuning.php - (c) TorqueCars