1: Exhaust - I want change the exhaust to akrapovic but i read that the exhaust give 5kw (if is true) and KTM duke 390 have 32kw
and for A2 max is 35kw, soo i will have problems?
I don't think cops have a tool to meassure the power of your bike if they control you. If you have to pass the revision just remove it and then install it again.
Also i wanted cut hole in the original exhaust for get better sound but i will lose my warrany by doing that?
Do just one thing, Akra.
...nice sound with just a hole! That's "smart"!...I tried this and I could feel that the bike wasn't performing well.. It lacked power! The start up and idling exhaust sound are great but at high revs it's just unbearable especially for a 125 so I re welded the whole.
2: I want buy the bike for fun and transport to work so i want ask if i will have problems/issues with new moto? how often breaks down?
How long is your daily commute? If it's long, consider that Duke 390 has a hard seat and for some people is not comfortable at all...and for other people the pegs position is worst. Ergonomic wise i think the Duke 390 is not the best bike.
I have no problems with my 390 yet, but i think is because my Duke is not an early model...i have read a lot of problems about the Duke 390 that has surprised me a lot. I think the problem may be the month/year of fabrication or! intrusive behaviour by users and bad riding habits.
You will have problems with any moto if you don't mantain and use it properly.
3: Do you think KTM Duke is good choice as first moto?
Short answer, yes. But it depends, there are several good first bikes if you look other brands. It depends on what you need and how much are planing to spend in papers, accesories and rider equipment. (You must explain yourself better so we can understand your needs)
If you are just learning how to ride...mmm, maybe it has too much power for a really new rider but it depends (years ago a friend of mine crushed his 400cc in his first attemp)...you can crush at the first corner if you are not used to it. Experienced people will tell you it has few power but consider they dominate the bike and you are just learning.
Sorry for my English its not my main language.
Don't worry, i don't speak english either.