check engine codes are
p0203,p0202, p0204, p0206, p0207, p0208, and p0121

Engine does not seem to be missing so I don't know why the first six codes.
The rpms will change suddenly when at and idle or just sort of coasting
(very little gas applied).

How do I check the throttle position sensor? Is it possible that there is a
common cable/plug for all these codes that could be causing the problem?

tia
jim