L300 Cooling water temperature: What is normal? Where is the petrol filter?

Hi, I changed the thermostat on the L300 (2.4 of 1991), had fluctuations in the temperature indicator: At the traffic light it went down, on the AB up etc. Always thought the 9 o’clock position would be normal (that I had on the AB with trailer), but with the new thermostat it can only go up to 8 o’clock. Is this normal (new QH 88° thermostat) During installation I discovered the between front axle and suction spider of the engine apparently the petrol filter is sitting, size like a 0,3 Coladose and above an Connection with hose (below probably also). Is my guess correct? If yes, how often is the filter changed? Do you change it from below? If the topic was already: the SuFu did not want to, could not browse in old posts Thanks Hermann