P39 misfire

I've had an intermitent misfire that i'm trying to diagnose. I think its the coil pack. It usually misfires when the engine is cold, but its started to do it at random times even when the engine has warmed up. I have disconnected the MAF, the engine cuts out immediately. I have also changed the plugs and HT leads.
It sounds like the left side has the problem but thats about as close as I can get to isolating the problem so far.
Any other ideas?
Thanks

did you let the engine warm up, befor you unpluged the maf senser..

Yea, it was upto its normal temp.

Should have also mentioned, it only mis fires while driving. If left to idle, it is fine.

you need to get some body to keep it running when you unplug the senser, then take it for a drive..

ok, i'll try that

Could be a head gasket on its way out. Check all the plugs for a rusty deposit. If you find one on 1,2,7,8 then its definite on its way out. Could be your coil packs, but more than likely a lead not pushed on hard on the plug

I've changed one of the coil packs. The misfire has gone but its still running rough. So I'm thinking that there's a problem with the maf. If i keep the revs up and unplug the maf the engine still runs the same. As there's no one here to help me I cant take it for a drive with the maf disconnected. Can I test the maf with a multimeter to make sure that it is the problem?