1989 Volvo 760 turbo problems

My 1989 Volvo 760 turns on sometimes right away and sometimes it doesn't it takes a while or i have to leave the key turned all the way until it turns on and when it turns on it idles ok and then it idles up and down and then settles and then it does it again, but it never stays stable it always idles. It seems like it is getting air but we checked all hoses and they are good. We changed spark plugs, fuel hose, distribuator cap, spark plug cables, and ignition rotor already. Nothing changed it still happens. Can it be a sensor? Also, it shifts good from 1st gear to 2nd, but from 2nd to 3rd it takes a bit too long I have to let go of the accelerator so it can shift. I've noticed when i accelerate fast and go fast when it come to shift from 2nd to 3rd it tries to shift but it cant until like the third or fourth try it shifts.