How To Change The TS Timing Belt
In detail, hope its helpful guys.
Alfa 156 2.0 TSpark Timing Belt Replacement
Repair Time – Remove and install 2.95 hrs
Camshaft locking tools – Alfa Romeo No.1.825.041.000
Inlet camshaft holding tool – Alfa Romeo No.1.822.155.000
Exhaust camshaft holding tool – Alfa Romeo No.1.822.146.000
Timing Belt tensioning tool – Alfa Romeo No.1.822.149.000
Balancer shaft belt tensioning tool – Alfa Romeo No.1.822.154.000
Disconnect battery earth lead
DO NOT turn crankshaft or camshaft when timing belt removed
Remove sparkplugs to ease turning engine
Turn engine in normal direction of rotation
DO NOT turn engine via camshaft or other sprockets
Observe all tightening torques.
Removal (numbers in brackets refer to attached diagram)
Engine under shield
RH wheel arch liner
Auxiliary drive belt and tensioner
Crankshaft pulley 
Timing belt upper cover 
Timing belt lower cover 
Cylinder head cover [5[
Center spark plug – cylinder no.1
2. Insert dial gauge in No.1 cylinder center plug hole 
3. Turn crankshaft slowly to TDC on No.1 cylinder. Use dial gauge 
4. Ensure balancer shaft marks aligned  & 
5. Ensure marks on belt aligned with marks on sprockets  & 
6. Slacken balancer shaft tensioner nut 
7. Remove balancer belt and sprocket from crankshaft 
8. Slacken timing belt tensioner nut 
9. Remove timing belt
Installation (numbers in brackets refer to diagram)
1. Ensure crankshaft at TDC on No.1 cylinder. Use dial gauge 
2. Hold camshaft sprockets. Use tool Nos. 1.822.155.000 and 1.822.146.000
 & . Slacken bolt(s) of each camshaft sprocket.
3. Remove third bearing cap from each camshaft  & . NOTE: Mark
Bearing caps before removal from identification.
4. Fit locking tools in place of bearing caps  & . Tool No.1.825.041.000.
NOTE: Ensure locking tools aligned with respective cam profiles to
prevent damage. Before fitting belt, ensure camshaft sprockets turned
5. Fit timing belt in ante clockwise direction, starting at crankshaft sprocket.
Ensure directional arrows point in direction of rotation.
6. Ensure marks on belt aligned with marks on sprockets  & .
7. Tension timing belt to maximum. Use tool No.1.822.149.000 .
8. Tighten tensioner nut .
9. Hold camshaft sprockets. Use tool Nos.1.822.155.000 & 1.822.146.000 
10. Tighten bolt(s) of each camshaft sprocket.
(A) Except 146: 100-124 Nm.
<B> 147: 108-132 Nm.
M6 Bolts: 10Nm.
11. Remove dial gauge and locking tools ,  & .
12. Fit bearing caps in correct locations.
13. Lubricate camshaft bearing cap bolts. Tighten bolts. Except 147L 13-16Nm.
14. Turn crankshaft turn turns clockwise to TDC on No.1 cylinder . Note: dial
gauge will need to be replaced.
15. Fit tensioner tool . Tool No.1.822.149.000.
16. Slacken tensioner nut .
17. Turn tensioner anti-clockwise until pointer  aligned with hole .
18. Tighten tensioner nut .
(A) Except 147: 21-26Nm.
(B) 147: 23-28Nm.
19. Ensure crankshaft at TDC on No.1 cylinder .
20. Align balancer shaft timing marks  & 
21. Fit balancer shaft belt and tensioning tool No.1.822.154.000 .
22. Turn tensioner until hole  aligned with center of tensioner . Tighten
tensioner nut .
23. Turn crankshaft two turns clockwise to TDC on No.1 cylinder .
24. Ensure timing marks aligned , ,  and .
25. Install components in reverse order of removal.
26. Tighten crankshaft pulley bolts.
a. Except 147: 24-26Nm.
b. 147: 23-28Nm.