Do a search on this . a lot of threads and good info/
Ive used it directly into intake through the PVC and by removing the air filter and spraying directly into the intake from the air cleaner box. CRC has pictures of it on Sonata before and after intake valves and pictures before and after of a mini cooper turbo and how it cleaned the impellers so it is fine to do it either way.
I have 40,000 miles on my 2.0 and have used it 3 times, I use top tier fuel but have also used BG 44k or Techron in the tank of gas before I do oil change (also I do the CRC before oil change)