The car is a 2000SSEi with 105K on it, it is having bucking/cutting out issues under boost pretty badly.
A bit of background, this car has had the LIM done by me (mechanically inclined) and after I did that it ran good for months.
Lately it has a problem that seems to be worsening, and need some input on what I should be troubleshooting. I finally did get an SES light and pulled codes P0102 and P0171. I cleaned the MAF and even though it seemed to run better the SES light would not clear even though I did so through the scanner.
I went ahead and bought a new MAF and after a few cycles of running and shutting off the light went out. It'* been smogged and passed with flying colors.
Anyhoo, here is what is going on. General driving staying out of the boost the engine will run normally and show no signs of problems. Under boost, as soon as you hit past that 0 on the guage the engine will start cutting out and bucking around. the harder you push it the worse it gets. The guage will show full 7psi of boost even though the engine is choking. And to add it will be at -10 at idle in gear and the gas mileage is normal.
Also, when the engine is colder and the outside air is colder it will not show signs of this issue until the throttle is near or at full throttle and will accelerate normally up until then. When the engine is warm, and outside temps have increased you can barely get into boost and it gets real bad. Even more so when the ac is on, I tried to pass a truck on my way to work tonight and had quite a bit of trouble just getting speed up, until I backed off and stayed out of the boost. It just wouldn't go.
I'm kind of stumped, help