i want to change my k03 with k03s(k03 with k04 compressor-180hp version). Is it ok to change it without changing any other thing? or i should change somtehing else? after that which chip tuning i should apply for k03 or k03s?

 

You wont see more than a 5-10 hp gain from switching to a k03s. If you are replacing a worn out k03 with a ko3s that is fine. But you can directly swap them and be fine, the differnce is minimum. As for chip, just the regular ko3 chip will work, they wont have a ko3s chip and a k04 chip will be to much.

 

will a 2001 s4 k03s fit in a 1999 a4? what i fine here in AF is that s4 has twin turbo and people say it wont fit. i am about to purchase a s4 turbo for my a4.

 

You may be able to use the chra and then use you compressor and turbine covers. Not 100% sure, need to compare where the oil/coolentlines go