EVOM tune and surging

[mbagge01]

I am hoping someone can help me narrow down my surging problem after getting an EVOM tune on my 2004 cayenne turbo. Car has 60k on it and coolant pipes have been replaced. This is what has been installed. EVOM intake, EVOM diverter valves, IPD plenum, leistung bypass pipes and EVOM tune which brings me to almost 600hp. In the process of trying to fix the issue, I have replaced the fuel filter, fixed various EVAP issues prior to the tune, replaced all the spark plugs and coils with newest OEM. My issues with the OEM spark plugs was getting surging almost at any time putting more than 50% throttle. Decided to change out to NGK iridium IX BKR6EIX plugs and narrowed the gap to about .025. Symptoms dramatically improved and now only issues around mid rpm range. Decided to go with a colder plug and used NGK iridium BKR7EIX plugs and get the gap as they came which is about .028 or so and symptoms are slightly better. On the first couple runs after I had put either of the NGK plugs in, no problems at all and it pulled hard. After the car warmed it, is when the surging began. Now it seems pretty consistent around the 3500-5000 range when ever I try to give it 2/3 to full throttle. The first drive with the car before it warms up seems much better and symptoms get worse as car is warmed up. I am not having any issues with idle or normal driving. I don't think it is a fuel system issue because wouldn't I see idle issues or other normal driving issues. Do I need to go even colder with the plugs or should I be looking for something else. On my durametric, no codes come up either throughout this entire process of changing spark plugs.