Unresolved

engine attributes and effect

You appear to be almost at the end of a 22 race season, your next race being the 21st race. You don't say what your core Fuel Economy, Tyre Economy or Handling design is. I imagine they will be relatively high given the number of races you have already completed.

Remember that the effect of adding design points is not linear, you will get a much greater benefit by adding 15 points to a core design of, for example, 35 (to achieve 50) than you will do by adding the same 15 points to a core design of 150. The higher your core design the less influential the supplier modifiers will be.

Also, driver errors are enabled for practice laps so it's nigh on impossible to use these laps to gauge the relatively minor effects of changing suppliers. Try running 5 practice laps without changing anything and you will almost certainly get a range of results spanning 0.2+ seconds. These inconsistent lap times will mask any benefit you may get from changing suppliers.

The effect of Tyre Economy is unlikely to show up in practice laps because, despite the community asking for it on many occasions, the Devs have so far not given us practice lap tyre wear to a decimal point. A change of 15dp is unlikely to result in the wear changing by an entire integer even from a fairly low baseline.

Fuel economy would have been negative 8 when engine is set to +Tyre Economy and zero when set to +Handling. Because fuel usage per lap is displayed to two decimals I am surprised you didn't see a change here. But like I said above the change will be minimal if you already have a high core design in FE. Please double check your Fuel Consumption.

Having your own engines will be worthwhile in the long term, but at the moment you are only getting a net gain of 7dp (+15 / -8) which is only marginally better than the standard game engines.