Stats:
2007 Cobalt SS 2.4L 5 Speed 60,000 KM's
Mods:
Vector Tune
Injen CAI

In the last 10,000 KM, my car after it gets warm at a stop light, clutch in, she will Idle around 1500 RPMS and creep close to 2000 and then drop back to 1500 RPMS. Now here's the crazy part!!!!.....****I let out the clutch a bit, so the engine grabs the clutch and then I put the clutch back in. Doing this, the Idle drops back down to normal RPM's. However the car's engine starts juttering and shaking, vibrating the whole car in the process, while the RPM needle stays the same****
Now I've for a while now have been getting the too lean code, because of my CAI, but it's never been a problem before....

What I'm thinking of doing is replacing the spark plugs and maybe the fuel filter.

Can anyone help me?
PS: Just got a call from the dealer who told me what I'm experiencing is NORMAL? WTF?!

 

I would say check your intake and TB area first. Maybe take off intake and clean TB and check air filter.

When I had the wrong setup on my TB i had a really high idle too.

The shaking is weird though.

Might be a bad fuel injector, i have seen that kind of shaking on a 2.2L

Any CEL ?

 

Update: It's fixed!

Turns out it was the Brake Cylinder Vacuum line, was rubbing up against something else, causing a hole in the line!
Swapped it out and put in a new line, shazzam! Just like new

All you 2.4L owners might want to check that line out as it loks it could happen to anybody.

 

Pics?

 

where are the pics?

 

The brake booster line comes from the rear of the engine bay and hooks into the side of the intake manifold.

Makes perfect sense by what the OP was describing. Just never heard of it happening.