V6 Rodeo Revs high on start.

Guys,

when I start the engine (3.2L V6 2000 Rodeo Manual) each morning lately, it leaps up to 2000rpm and takes about 30sec to gradually come down to 750rpm. It didn't use to do this before. Summer over here (Australia) at the moment, so not a cold start thing. I've also had the odd stall at lights occur. This happens mostly after some rapid acceleration and then stopping quickly. The rpms bounce a few times then die. Any clues?? Should I just reset the ECU and see what happens?

Thanks,
Wayne

yup it is a leaky IMG (Intake manafold Gasket)

http://isuzufaq.ibctech.ca/#faq5