my idle will alternate between 900 and 650 rpm

not as in it constantly bounces up and down but as in on one trip it will idle at 800 rpm, take it for a spin an hour or so later and the idle will be at 700 rpm

and at the lights when i go into neutral it might bounce down to 600 before bumping back up to 750.

any ideas? its just frustrating that all is not perfect.

it is a manual ef xr6 wth an impco gas setup

cheers

and if anyone knows additionally.. it i sit at 100kmph in 5th gear at 2000rpm, is my diff a 3.45? thanks

Give the idol air control a clean. It sits on top of your throttle boby. Spray some brake clean into it, off the car of course, and see if that helps. Easiest way to check your diff ratio is to jack the diff up put a mark on the pinion and on the tyre, turn the pinion one revolution and count how may rotations the trye makes eg 3.45. The amount of rotations the tyre makes is the diff ratio.