Mechanical Fault with Toyota Avensis

in case i am wrong you can use this link

http://www.toyotaownersclub.com/forums/lofiversion/index.php/t16378.html

check the compressions of the cylinders.

remove the exhaust befor the cat and see if problem is still there, reason if valves are burnt there would be unburnt fuel going past valves and unburnt fuel causes lots of damage to cats, and they block up giving a rise in back presure in the exhaust noticable by lack of top end power Its bad when your cats blocked

I cannot imagine why a mechanic would dismantle an engine and only grind two valves, totally crazy and a waste of time and money.

Your mechanic is not working well for you, or you are over controlling him.....

Remember, some people "save money no matter what it costs!"

Logically if two valves need this sort of attention, then the others are not far behind, so the whole cylinder head should have been serviced fully.

1) Check block for flatness, especially in the area of the damaged gasket.

2) Light skim of the head to assure flatness. I did this once and found that in all I had to take off 1mm to get the head flat agin. Mitsubishi Diesel head......

3) All valves reground and lapped in.

4) Check for broken/damaged/loss of tension valve springs, maybe replace all.....

5) Re-build of head......all clearances of all valves checked, though I suspect it has oil lifters, I have not got much personal experience of these, but possibly some are worn?

Check the exhaust sensor, may have become contaminated prior to head works by non combusted fuel. Sensor failure would put the engine management system into fault mode