I am currently having this type of problem as well ,
My car just got a new opti and 2 weeks later this started

The elbow is ripped on my car so I ordered a 1LE and I am hoping that the rip was causing un-metered air to get in to the intake thus causing the MAF to cause problems / throw a code

My car also shifted a little wierd at times and if I get on it under a load it bogged and makes a " clicking " noise under the hood , Mine also is more frequent when the car is warm

 

well i have the Vortech all metal elbow so that is moot point there about mine ripping

 

I had very similar issues with my car and found it to be the waterpump leaking a small amount of water onto the right bank of the opti and causing some MASSIVE misfire problems once the temp came up, i am guessing it was due to some seal letting go once the temp came up.

 

well i havent put it all back together yet with the new opti but it runs good, idle is around 1100 on start up, and it seems to rev good and quick. it was idling around 1600 yesterday which sucks when you put it in DRIVE! but as soon as I was in gear it came down to 800 or so and stays there just fine, it was only when cold and at idle

 

I got to thinking and it could possibly be a vacum leak. I had a problem similar to that when my plug i had to cork up the silencer hole on my intake bellow came out. It sputtered and bucked and wouldnt even run. A small leak would cause the same thing but not as bad, and the car would run. Check all your intake boots and hoses and make sure nothing has a small hole to let un metered air in past the MAF. This could be way off but its one thing you can check off the list.

 

there is no way at all that unmetered air could be passing the maf. I have a Vortec polished elbow in there and that things hard as hell to just put the maf on much less letting air in

 

well i pulled the fuel rail today being as it wasnt building enuff pressure or even holding pressure after the key was off. I bet it was getting about 15 psi. the stock regulator was nasty! all clogged up in the strainer like the the stock injectors were with rusty looking gas and chunks of crap. I think I found most of my motors issues right there. I think the stock replacement pumps were pushing too hard and straining and going under way too fast. This hoe should be a screamer tommorrow! here I come mustangs

 

well i went to go get the sender unit and had to take a ride in my buddies ford truck. This is one of those Ford dominate , always talking about how good they are, how bad Chevy is kinda guys. Well after we get it, the right front brake caliper locked up and I was stuck in the back of a truck, getting rained on, while its sliding down the road with 3 wheels moving