Engine losing power under load - 2003 Mitsubishi Pajero IO 4G94 4DR

I own a 

2003

Mitsuishi Pajero IO

1999cc 4G94

Chassis: JMYLRH77W3Z00480

The vehicle started to lose power while I was going up hill. I've noticed that it happens from time to time while on a flat as well when I'm moving off. It works fantastic in the upper RPM even between shifts while the momentum is up at higher speeds. At lower speeds it feels almost as if it's going cut off because it does not step down in gear smoothly all the time. What could be the possible issue since the transmission was recently serviced but I believe they only did a flush and not tan actual service as in inspection and proper test drive etc. Any suggestions or thoughts from anyone? I would really appreciate it also if anyone knows of a location where I can purchase a transmission overhaul it. I only have 48,000KM on the ODO. Also if anyone knows where I can find a suspension bushing kit so I can replace all rubbers to hep the situation..... HELP!