i have a p08 ecu on my d16z6 when connected tthe ecu is coming on with a check engine light but i do not have vtec wired up at the moment is that the reason for the cel or is it the o2 sensor throwing the ecu off. i know my d16z6 has a 4 wire o2 and the d15b has 1 wire 02 sensor; also is it good to use the different ecu ?

Pull the code(s); it could be vtec, O2, or both. The general rule is to always use the ECU for the engine you have.

also is it good to use the different ecu ?
no the p28 is the best for the d16z6