That hole on the other side of the head is the sensor for the VVT. They are really not expensive, just hard to find. Go to WWW.RHDJAPAN.COM . They had em stock for like $25 the last time I checked.

Wow! Well, apparently, it has been a while since I checked. They are now $125 shipped. The price went up. Inflation sucks. I would look elsewhere. Good luck.