2008 Saturn Vue XR V6 AWD Help!

Hello, I have been experiencing some
issues with my 2008 Saturn Vue XR
V6 AWD. Had it for about a year now
and has 140,000 miles on it.
Anyways, it has been chugging and
speeds around 50-60 miles an hour.
Doesn’t always do it but often
enough to notice it. Ran codes on it
and popped up P0013 camshaft a
sensor and P0014 camshaft B sensor
timing being out of whack. So went
ahead and replaced all 4 camshaft
sensors only to find that the P0014
camshaft sensor B code still persists.
Took it into the shop to see what they
thought about it and they ran there
codes on it to see that it has these
codes currently popping up: P0014
Exhaust camshaft position sensor
performance bank 1, P0430 catalyst
system low efficiency bank 2, P0L10
intake cam position system
performance bank 1, P0024 exhaust
cam position system performance
bank 2, and P0306 misfire ran down.
They have recommended pulling the
valve cover off to check the timing
which said will cost around $350 just
to look at. Looking to gain some
advice on where I should take it from
here and to see if somebody has had
a similar instance where it was able to
be resolved and what something like
this might cost? Still have about 19
more payments left and not wanting
to get another vehicle if possible.
Also don’t want to spend money on
needless repairs.