Mga sir magandang araw po sa inyong lahat!
Recently lang ng engine swap ako for my civic from ph15a to d15b dual vtec. All went well naman at na road test ko and it seemed ok although i noticed na mababa you idling niya somewhere between 400-500 rpm. Well anyways apart from that certain change i also noticed that hindi kinabit yung O2 sensor kasi there was no slot for it provided that i am using aftermarket 4-1 headers. Hindi rin ako marunong to check for the vtec if it is functioning properly.

Mga sirs if i could solicit some of your time and expert opinion regarding the following:
1. Normal lang ba na ganun yung idling niya for such an engine?
2. Wala bang negative effects kung hindi ikakabit yung O2 sensor? (eto ba yung sensor na sa exhaust manifold?)
3. Will the engine still be able to do 12-valve lean burn mode kahit wala yung sensor (O2)?
4. How to determine if the vtec function is working proplerly?
5. Lastly would i get a check engine light if vtec system particularly yung banda sa head like solenoids,pins,cams,etc? (what are the visible symptoms of vtec malfunction?)

Mga bossing i hope na matutulungan niyo po ako sa mga queries ko po, newbie lang at willing to learn.
Thank you very much po!