Help please? engine management system

[kyriss]

Good mornin All, I'm very new to this but hope you can help. I have an old Hilux Surf, K reg. which has been messed about with like you wouldn't believe! It's now gettin sorted by a proper machanic but timin is still a problem, and the red light is on almost permenantly, untill turbo kicks in but not as good as it shud be. The loss of power is intermittent and so frustratin. Does anyone have a clue as to how to discover what the real problem is?

Thanks muchly for readin, Chrissi