I had trouble with tank sensors years ago and was directed to HC Extreem. You're right about it being pricey but I can tell you, if you follow the instructions to add it into the tank and go for a drive like it reccomenends, it will do the job. At least it did for me and I've been a HC Regular user since.
Don't be shy about going for a Long Twisty drive. I think that's part of the secret.
Dennis & Carol
2003, 4006, 41' DutchStar,
Spartan, ISC 8.3L W/BanksPower - 2013 Honda CRV, BlueOx Baseplate, Aventa Bar & Patriot Brake. And the 04 Bird, Sunshine Car.