How to solve the obvious fuel consumption after Fox maintenance?

First of all, you must understand what you have repaired and adjusted, and then you can prescribe the right medicine. Your question is like saying, "I'm sick. Tell me what's wrong." Even the imperial doctor can't know and answer you.

The increase in fuel consumption is generally manifested in several main aspects:

ECU stroke computer adjustment (electronic adjustment). The amount of fuel injected has increased. One of the adjustment methods commonly used by Fox, in order to avoid idling jitter caused by dirty throttle, many repair shops have encountered such simple adjustment to achieve the effect of avoiding idling jitter. The negative impact is an increase in fuel consumption.

There are faults in the vehicle running system (running system), such as insufficient tire pressure, lack of oil or damaged wheel bearings, inability to release brakes, deformation of suspension system or other factors that affect normal work, resulting in increased resistance and increased fuel consumption.

Mechanical problem of the engine, excessive wear, insufficient breath holding of the cylinder block, incorrect ignition timing, frequent short-circuit of VIS and incorrect valve adjustment will all lead to increased fuel consumption.

Excessive wear of gearbox and clutch leads to clutch slipping, which is also one of the possible factors that lead to useless engine and increased fuel consumption.

You can also have a look at these aspects I have casually mentioned for your reference. Please go to a professional repair shop for specific reasons.