The sensor is on the thermostat body and I unplugged it when hot, no change.

The sensor sends to ECU and ECU to dash...

It's running better now I've stripped and modified the pickup module in the tank.

Poor design on the volvo means it can suck air even when there is 1/4 tank left.

Update, looks like Ford use the same in tank pick up unit. if you are seeing bubbles in the fuel line and have 1/4 tank or less you have sediment in the fuel tank, blocking the only 3 mm hole that allows fuel into the fuel line...