Timing marks needed

If you have a vacuum gauge, attach it to a manifold vac source, then raise the idle to 2000 rpm, watch the needle, if holds steady at 18-22 hg the exhaust is clear, if the gauge drops, the exhaust is clogged. Also test fuel pump pressure.

Possibly the timing is off Check this way: 1. Connect NGS scan tool to DLC-2 located under left side of instrument panel, right of steering
column. See Fig. 12. Connect a jumper wire between terminals TEN and GND at DLC-1 in
engine compartment. See Fig. 13.
2. Ensure idle speed is correct. See IDLE SPEED under IDLE SPEED & MIXTURE. On all
models except Millenia 2.3L, connect timing light to high-tension lead No. 1. On Millenia
2.3L, connect Inductive Timing Light (49-T018-002) lead to ignition timing checking harness
(Black/White wire) located next to engine compartment relay box. See Fig. 11. Start engine
and allow it to idle. Check timing. See IGNITION TIMING SPECIFICATIONS table. See
Fig. 14.
Fig. 11: Identifying Ignition Timing Checking Harness
Courtesy of MAZDA MOTORS CORP.
3. On all models except Millenia 2.5L, if ignition timing is not within specification, check CMP
sensor, CKP sensor, TP sensor, ECT sensor and transmission range switch. See appropriate
SYSTEM & COMPONENT TESTING article. If all sensors and switches are okay, replace
PCM.
4. On Millenia 2.5L, if ignition timing is not within specification, loosen distributor lock bolt.
Rotate distributor until timing marks align. Tighten lock bolt. Recheck timing.
NOTE: Standard inductive timing light may not work on ignition timing
checking harness. Recommend using manufacturers Inductive
Timing Light (49-T018-002) or equivalent.

Well I was talking about setting the timing, not installing belts. But here it is
Put #1 cylinder at top dead center, then the marks should align this way. ALWAYS install a new tensioner the spring gets cut cover time and WILL FAIL, MAzd has an upgraded spring now.
1. Ensure all timing marks are aligned. See Fig. 10.
2. Install timing belt around crankshaft sprocket, water pump sprocket, idler pulley, and camshaft
sprockets. Ensure slack does not exist on idler pulley side of timing belt.
3. Complete timing belt installation on slack (tensioner) side. With tensioner spring removed,
allow tensioner to ride against timing belt. Turn crankshaft 2 revolutions in normal direction of
rotation (clockwise). Ensure camshaft and crankshaft timing marks are still correctly aligned.
See Fig. 5. If not correctly aligned, timing belt will have to be removed and repositioned.
4. If all timing marks are okay, turn tensioner clockwise using an Allen wrench. Connect
tensioner spring to pin on engine block. See Fig. 11. Turn crankshaft 2 revolutions. Ensure
camshaft and crankshaft timing marks are still aligned. See Fig. 5.
5. To install remaining components, reverse removal procedure. When installing valve cover
gasket, apply small amount of silicone sealer to 4 corners of gasket where the front of both
camshafts go through cylinder head. See Fig. 12. Tighten valve cover bolts to specification in
correct sequence. See Fig. 13. Adjust drive belts to proper tension.
6. Inspect crankshaft position sensor air gap. Air gap between outer edge of crankshaft pulley
rotor tooth and center of CKP sensor should be 0.029-0.059" (0.5-1.5 mm). See Fig. 14. Air
gap is not adjustable. If gap is incorrect, check for damaged parts.

1. Ensure all timing marks are aligned. See Fig. 10.
2. Install timing belt around crankshaft sprocket, water pump sprocket, idler pulley, and camshaft
sprockets. Ensure slack does not exist on idler pulley side of timing belt.
3. Complete timing belt installation on slack (tensioner) side. With tensioner spring removed,
allow tensioner to ride against timing belt. Turn crankshaft 2 revolutions in normal direction of
rotation (clockwise). Ensure camshaft and crankshaft timing marks are still correctly aligned.
See Fig. 5. If not correctly aligned, timing belt will have to be removed and repositioned.
4. If all timing marks are okay, turn tensioner clockwise using an Allen wrench. Connect
tensioner spring to pin on engine block. See Fig. 11. Turn crankshaft 2 revolutions. Ensure
camshaft and crankshaft timing marks are still aligned. See Fig. 5.
5. To install remaining components, reverse removal procedure. When installing valve cover
gasket, apply small amount of silicone sealer to 4 corners of gasket where the front of both
camshafts go through cylinder head. See Fig. 12. Tighten valve cover bolts to specification in
correct sequence. See Fig. 13. Adjust drive belts to proper tension.
6. Inspect crankshaft position sensor air gap. Air gap between outer edge of crankshaft pulley
rotor tooth and center of CKP sensor should be 0.029-0.059" (0.5-1.5 mm). See Fig. 14. Air
gap is not adjustable. If gap is incorrect, check for damaged parts.
Also CHANGE the tensioner or you will do the job again!
Put #1 piston at TOP DEAD CENTER.

Is the number one piston at TDC with marks lined up? If it's a bottom, timing is out by 180 degrees. Also if either sensor was damaged during the swap it will cause this.

If the motor is fuel soaked so bad that gas is sitting on the pistons, a plug, oil and filter change is needed, then check for fuel in the pressure regulator vacuum line, if there is any, replace the regulator.

Good work!