Dear all, my Mehran is suffering of Missing problem badly on Petrol and Gas both.

My machenic have checked the following things yesterday;

1- Replaced Plugs and Leads
2- Replaced Point and fix timing from distributor
3- Fixed Tapets
4- Checked Coil
5- Checked mixing

Everything is working fine

Or to or us duffer nay distributor say timing out kara kay bar bar patakhay bhi nikalay hain carburator or silencer say, and becoz of it silencer phat gaya hay or flames ke waja say carburator kala ho gaya or mohallay walay dar gaye becoz of horrible sounds.

And finally he said carburator or plugs saaf ho gaye hain
But after some stability the car starts missing again.....

Experts tel me what can b the reason behind it ????
Is there possiblity of burning of valves and seals?????