stock turbo malfunction??????

[speedracermage]

ive has my sr motor for 3 years now its only been driven for about a year now due to project funding. recently i have had days where the turbo wont function almost at all. there have been other days that the turbo wont create enough pressure to set off the bov. and days where it will be just fine. mind you it is winter and has been cold and i allow my car ten minutes to warm up before i run it... any ideas. i am no expert mechanic but i have been competent enough to do the swap, the wiring, my exhaust, droping the car as well as my wiring. so please go into as much detail as you can if need be.