My 02 protege5 (127000 miles) has a manual transmission. Once I left the 1st gear in and forgot and suddenly releaseed the clutch. And the engine went off after a jerk. From the second day on, there was a spark knock when I applied too much gas. Then I added some fuel system cleaner to the fuel and put two tanks premium gas. Then the check engine light went on and the code shows lean in bank 1. After two tanks of premium gas, the spark knock almost disappeared. I reset the ecu two more time and it still on. I think something is wrong. If the sudden clutch release caused this, it would be timing belt, right? Someone suggested to change fuel filter and clean the egr. I don't think I can change the fuel filter with ease. Anything I can do to solve or locate the problem? Thanks a lot!

 

Shouldn't you get a new timing belt around that mileage anyway? It might have jumped a tooth but it's too hard to tell with out looking at it.
A lean condition typically comes form un-metered air getting in, or not enough gas. Check for vacuum leaks first and clean the MAF sensor. The accordeon like snorkel gets brittle over time. Bent it to see if there are cracks. All the vacuum lines ought to be checked and if the ends are no longer flexible replace the hoses, it's cheap enough.
Also look at the spark plugs. The whiter they are, the leaner the mixture. If only one of them is white it's likely the lower intake manifold gasket taking the blame.
Not enough gas: fuel filter, fuel pump and fuel regulator are key. The fuel system is under pressure. To relieve the pressure on my '98 Protege I have to take out the rear seat to unplug the pump, then run the engine until it runs out of gas.