Would help to know the title of that code...
Piggyback rail gauge no bueno.
I've always heard and thought its best not to introduce a possible interference/interruption in the harness. Best rail sensors are OBDII based in my eyes. Then you know exactly what the ECU is seeing. Just one more set of variables when you piggyback. Gauge can malfunction or worse... its reading correctly but interferes with signal to ECU. Not saying thats whats happening with you. Just saying, I've definitely seen many scenarios where it was the culprit.
Gostman, my t/c output shaft has about the same play up and down . I was gonna look at a schematic and see if I could just put some more torque on the nut and take the play out . I got 302k on mine but I’ve had a free spin kit since 70ish k.