Lumpy Idle

[Awsniper]

I have a 97GST that has been sitting for about 2 yrs. On ocasion i would go out and crank it up. Just last month i crunk it before i went on vacation to guam, and when i returned to sell the car, crunk it, and i had a very lumpy Idle. Idle holds at 850rpm, and Vac shows about -12. I gave the car a little gas to see if it would kick over, and white smoke car from the exhaust. I have done the search on the White exhaust ( Oil, or Coolant). IF there is a blown head will this cause lumpy idle? Turbo only has about 60-100miles on it. No shaft play in or out, and spins freely, and have not done compression test yet.
Any other Ideas?

 

[Awsniper]

I removed GM maf, replaced with stock MAF, and still have the same lumpy idle. Vac holding at 15. RPs at 850-900. No cel only. SRS light and Safc set to 0 across the board.
My fuel pressure is at 44. Stock injects. when reved, it stumbles to stay on once back near idle, and sometimes backfires.