06 4.8is - anyone else have trouble with this?

I know they act up sometimes on all BMWs but this is really driving me nuts.

Have reset multiple times after adjusting to OEM door sticker value using digital gague, both cold and even tried warm.

Goes away for several days then returns.

Any advice? Hate to see the dealer about this, despite CPO -- they will assume the first couple of trips it just needs air adjustment.

Also --I'm assuming it's a sensor based and not ABS system? Anyone know if I can buy an aftermarket TPMS console that will read the existing stock sensors already in the wheels so I can read the actual PSI for each wheel?

Or I woud install a complete aftermarket system but then I'm afriad I'd always get the warning light since it would miss the values being transmitted from the OEM sensors I'd removed to install the aftermarket ones.

Any advice on this greatly appreciated -- thanks!