TLDR: Can I resync the throttle pattern without going to a dealer/mechanic?

For the past couple of months I've had a weird stutter on my 08 G35x. Nothing violent but it just feels being lightly pushed back and forth with an associated noise from the engine hiccupping a bit. There is no engine light however and the RPMs are constant while this happens. You can instantly stop the stutter (at least for a few seconds) by either increasing or decreasing throttle. So it isn't a constant problem and seems to occur most frequently when going uphill or a on flat but not while going downhill.

The stuttering only happens in 3rd gear or above and generally above 80km/h. It also seems to be temperature dependent as well because it takes a while to appear. In the fall with moderate temps it would occur within 5-10 minutes of starting, but in the winter at subzero temps it won't start happening until 20 minutes down the road. Stranger still, driving the car in manual seems to increase the speed threshold at which the stutter happens. For example in 5th on AUTO it will stutter anywhere around the 80-100km/h range, but in 5th MANUAL it won't stutter until around 115km/h+. It does depend on the gear selected though, so going ~100km/h in MANUAL 4th gear will still have a stutter.

I did take it to the dealer and they scanned it but got no codes. I thought it might be a transmission issue initially but they found that the transmission shift pattern was "as per spec". They did find that the throttle pattern was "not in sync" however and found cracks in the intake tubes (normal wear and tear) and wouldn't diagnose further until those were replaced. So I bought and installed some aftermarket intake tubes but the problem persists unchanged. So is there anything I can do myself to resync the throttle pattern, or do I need to shell out at the dealer again? I'm open to any other diagnoses/ideas.

 

I would also check the PCV hoses, it sounds like you have a vacuum leak, causes a bit of a hesitation when applying throttle.

The APP and TP recalibration are just to reset them to the zero stop position.

How many miles are on the plugs?