Check if you have an air leak somewhere on the intake, you can use startgas, you spray along the intake pipes and hoses, listen for if engine change rpm.
Usual places where it can leak.
-rubber hoses that connect between the intake plenum and runners
(they can look brand new but be badly cracked underneath).
-intake runners are sealed against the engine with an O-ring which can be cracked and/or
have begun to creep out of their seat/location.
-hose that connects to the turbo from the pipe coming from the AFM.
Check also dump/diverter valve so it is not a small crack/leak in the membrane inside it.
Is the new crank sensor fitted to the right distance from the phonic wheel ?
Did you check the distributor cap ?
Try disconnecting the lambda sensor when the engine is warm so that the ECU are running
in open loop and see if it makes any difference at low revs.
Check the connection for the temp sensor to the ECU so that it is OK.
Be careful with Shell V-power (test with just a bit in the tank so you can easily dilute it),
for some mysterious reason the TB engine seems to run really bad with that fuel.
No coilpack's on the TB, just one ignition coil and distributor cap with HT leads.
Hope this can be of some use.