^ you need that oil pressure sensor there. vtec runs of oil levels, temp, and oil pressure. that sends signals to your ecu and your ecu tells you if your oil level is to low if something is wrong. if your motor is not warmed up then vtec wont kick in, same as oil level. if its to low or to high then it disrupts the flow and wont let vtec kick in. like if you dent a oil pan on a vtec motor it disrupts the flow and causes problems for you vtec. like i said i think they make a thing that goes on your oil filter now so you dont have to drill into the block but thats just my