2007 Isuzu Crosswind XTi Stalling problem

Have a problem with my Isuzu Crosswind XTi. Around late November last year, I noticed a problem with my Crosswind which steadily and progressively worsened. It started out when I felt there was a slight delay when I started the engine. This then progressed to it wouldn't start at the first click of the engine but second and later on maybe third or fourth time I switched the ignition on. Then when I was driving it, I felt there was a feeling of sluggishness during the early days of the problem until it worsened to the point where on drives the rpm would go down and the engine stalls and I would stop and need a minute or 2 to start up the engine again. It progressed to the point where I would stall 3-4 times.

On December 29, 2012, I decided to have it serviced at Isuzu EDSA Balintawak. They managed to fix it and told me it possibly was a belt problem. So for a month and a half I used it normally until this Thursday Feb. 14, 2013 when I felt the delay again and today, I noticed the symptoms I described above coming back. I will be bringing it back to Isuzu EDSA Balintawak again tomorrow but I would like to know if anyone has had this problem and what could be causing it. Last December, they parts they replaced were the following:

1. Gasket, drain plug;
2. Plug, drain, fuel tank
3. Oil filter element
4. Fuel filter element
5. Belt, cooling fan
6. V-belt and
7. Repair Kit, CLU slave cylinder.

It's a 2007 model and not much smoke is coming out so not sure if it is calibration related. Hope people can help me diagnose the problem.

Thanks in advance!

Best regards,

Dex