[bluedog]

I'd propose to do it in the following order:

- new spark plugs
- ignition timing test
- Engine control unit memory scan (read out error reports, if any present)
- check ignition coils
- compression test
- Fuel pressure check
- valve clearance inspection
- Octane booster

I come to that order by asking, what could cause engine noises.

For that it needs a bit more than bad fuel or low fuel pressure, so lets do that after we run out of more probable Ideas...

First, lets take care of the ignition. That takes the power out of the fuel. Then, see if the engine mechanically is ok. That means a compression test.

Give it a set of new spark plugs, just to make sure, ignition isn't the problem, and because you don't need any special tool. A 16mm plug spanner will do...

Then, if the problem still persists, check ignition timing. I think, that must be ok, because if not, you would not get >140km/h out of the Engine... it would maybe not even start. But, it is a test which doesn't take to much time and any mechanic should be able to do that.
If the engine Timing is wrong, there must be a problem with the timing belt or with the camshaft/crankshaft position sensor. You can't adjust ignition timing, so if it doesnt right, you know where to look for the reason...

If that is ok, go to the Daihatsu dealer and let him read out the ecu's memory. If there's errors reported, you get a hint where to look for the solution.

At this point, only the ignition coils rest from the ignition System.

If they are ok, lets think about fuel pressure. If the mixture is too lean, you have power loss, and if you have the pressure gauge and know what to do, it is about 30min. of work only, and you don't need to buy any gasket or other spare parts just for test.

So, either you look after the mechanical part (valve clearance, proper compression rate) but you'll need a pro for that, because you probably do not have the tools... It would mean some real work, anyway, whilst before, everything was quick and easy to check;

or you can try octane booster, now that you are sure the ignition must work.

If nothing helps, there is still the MAP sensor left...