hi and welcome to just answer.
The engine control module does not need rebooting.
after the timing belt was replaced did you notice any difference in performance idling and noise?
Have you had any warning lights on the dash no matter how brief.
do you know anyone who has a code reader with live data on it?
what is the current fuel economy mpg?
the timing belt replacement may be the issue the camshafts sprockets on this engine
have to be locked with a special tool the 3 centre bolts loosened this is to ensure that it is timed accurately even half a tooth out will not produce any fault codes but will affect fuel consumption.
there other items that can cause a reduction in fuel economy and need to be assessed using a live data reading via a diagnostic scanner this will also pick up any recent fault codes stored in the computers memory.
things to do next.
check the timing.
check the engine coolant temp sensor reading on live data at running temp to see it corresponds with the gauge .
check the mass airflow meter intake air temperature reading at running temp.
these are the main areas to check .
I will hit the answer button but you do not have to rate it yet and can continue to work with me on this.
I will look forward to your reply.