RadioFlyer

Another option is to extend the intake with sections of the Y pipe to mount the filters onto. I've thought about doing this, but never really needed to. But my thought was to buy piping from Pep Boys or Home Depot, either a 3" exhaust pipe section, or pvc from the plumbing section, and cut it into two 10-12" pieces, and get two silicone couplers. You're still pulling from right in front of the radiator, but the filters would be on the right-side of center instead of the left-side. But you'd have a decent length of straight pipe before the MAF takes it's reading, so it would eliminate this variable.

Caveat here is that I don't use the Stillen heat exchanger, so the front of my radiator is the same on both sides. YMMV if you're using the Stillen unit.

Another comment, about how it happens more when the car is warmed up, have you guys monitored IAT (Intake Air Temp)? I monitor that on my car, and it heatsoaks really bad when sitting in traffic, or if the car is parked for 30mins to an hour. What I've seen with ambient temps around 80*F, is that if the car is warmed up and driving around, the measured IATs are about 5* higher than ambient. But when you park and get back into the car, IATs are commonly in the 120*F range. Sitting in traffic, I see around 105-110* IATs. This results in whacky fuel trims, definitely different fuel trims than IATs in the 80-90* range when the car is just cruising without traffic. The constantly changing fuel trims seems to be a source for the idle surge for my car. In other words, the car hunts for a way to stabilize AFR at 14.7 while idling, and it does this by adjusting the fuel trims.

My current running theory is that the ECU is logging the fuel trims for each condition it sees (idle RPM/high IATs), and eventually, it will have the data stored, and it will just go to that fuel trim and idle correctly the next time it sees the same conditions. It's sort of playing out like that, but not perfectly. I'm trying to give it more time on this reflash.