My 97 Malibu, 2.4 was running rough. Replaced both O2 sensors. Car started to run great for about a week. Gas cap was lost and check engine light came on. Replaced cap and light went out after about 30 heat cycles. Car ran great for about a week. Now engine light back on, occasionally stalls when transmission has torque applied, runs rough.

Any ideas? Is there another sensor I should replace? There are several on this thing.