2002 saturn sc1

have a 2002 saturn sc1 1.9 4 cyl. 5 speed single overhead valve.

bought it new has 112,000 miles.

ck eng light came on high idle. vacuum leak number 1 cyc

pulled off entake manafold, replaced intake gasket, number 1 injector,

started up all ran fine for about 2 weeks

chk eng. light came on . bought a code reader \
got po 172 eng. rich bank 1

changed oxgen sensor, at front of eng.

code came back on po172 eng rich bank 1

changed three more sensors. still came on . took to shop checked cat. said was ok

took to another shop , kc martin, lynnwood wa.
said they could find nothing wrong, might need computer flashed, took to dealer, flashed computer, still comes on p0172 eng. rich bnk 1

I cant figure what to do next.

I put out the ck eng, lgt. and it stays off for about 1 to 14 days, comes on and goes off while driving.

any suggestions.
thank you
Ron