when i rev my xr6 to any rpm then take my foot of the accelerator the revs drop down to 100-200 rpm,would anyone also be able to tell me if it idling around 600-800 rpm mark is normal(would be able to say exact rpm it idles at but that involves going down to my car),it recently got all spark plugs and some other stuff replaced
thanks

you will have a severe vacuam leak somehwhere.
check the pcv valve and your map sensor.
in neutral the idle should sit on about 6 - 700 rpm

I agree there, same thing happened to me, it was the pcv valve. But check all your vac hoses for cracks and flared ends, sometimes the hose may be on but the end is stretched and lets air in.