Spark plug help

[badgerboy]

Hi.

I read someone, possibly Silvia God's site that you shouldn't fit Champion spark plugs on a ca18et. Is this true as mines got em and I've still got idle problems. It will idle fine for at least 10 secs then drops so low it eventually stalls.

The timing, air meter, idle switch are ok. No air leaks, vacuum hoses ok, etc..
Plugs aren't oily and were fitted new when engine rebuilded, HT leads are new and tested fine.
ECU displays 31 - no fault as got no air-con.
Fuel pressure spot on had recent filter installed, temp switch ok, injectors tested ok, wiring ok.
When you rev the engine it doesn't stutter and is fine, so I'm a bit stumped

If anyone's got any suggestions I'd be grateful as always !

Thanks
Si ;-)