Rough idle (sometimes), exhaust puffing noise when rough on 1995 Toyota Corolla

Replaced fuel pump because engine would quit & trouble shooting revealed not fuel pressure. Now eng idles rough sometimes when stopped and seems like it may quit. Replaced plugs, cap, rotor. all seemed worn.
When eng is running rough and varying RPM FROM 700 to 1200 there is a puffing sound from exhaust like a miss fire. Rev the eng and it all goes away.
Think it might be EGR valve? Timing belt?

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1 answer 1 comment
EGR normally fails to operate on the Corolla rather than sticks open. Pull up the spark plug wires and see if there is any oil down the plug tubes if so remove the valve cover replace the V/Cover gasket and spark plug tube seals. For good measure check the valve clearance they are shim adjusted and no one checks them. Are the plug wires OK? Any oil inside the distributor cap, I have seen oil inside the cap cause rough running.
Thanks for ideas. Will ck valve clearance. This problem came on all at once, that's why I hadn't given valve adjustment a thought before.
Plug wires are good & no oil on wires. Valve cover good. Also, no oil in dist cap when I replaced it.