Aramith these guys are right and also cheeky with there comments because they come across new members asking and stating the same thing from time to time.
you can do a search on youtube and find some crew doing test and debunking these cheap power increase mods.
I've had the V35 the V36 and now the V37. They all cost alot of money to make more power, V37 a little less because it has a turbo and a tune does help alot, But done by a professional. I was quoted $1400 for a tune (extra 35hp at the wheels if i'm lucky)
your best power increase for your car will be a full exhaust and a better air intake