CGI Valve Sticking?

If the CGI Valve is sticking, would this produce a momentary exhaust leak type of sound? Or the sounds of valves sticking? How can I check for leaks? Upon acceleration when the engine is warm, I get a momentary loud engine noise like something sticking open as though a valve is open then it slams shut as though something sucked it closed. At first, I thought VVA or IVA. The VVA was replaced twice because IVA 4 was low. The second VVA made IVA 6 act up. What about bad wire harnes in the head? Could it be grounding out? At the same time, the idle pulses while driving and never when sitting. They do not occur without the other which leads me to believe the CGI valve is sticking when warmed up thus causing the ECM to produce too much or too little CGI or an exhaust leak of some sort. If the VVA was sticking, wouldn't this produce a code? There are no codes at present. SDP engine.