Lately my vyss has issues on initial cold start up. It will start straight away, idle normal for a 20 seconds, then spike for a second or two, then back to normal. Once I put in drive, it will surge & stumble for a few seconds then get a check engine light with fans on. Ten seconds later, light & fans switch off & all good. No problems after that & drives normal but will do it again the next cold start. It has new spark plug leads & wires. I used a scanner to check for codes but showed nothing. I can't see or hear any any vacum leaks.I don't drive the car much as I only use on some weekends. The mods are cam & heads, full exhaust & otr. Has anyone had a similar problem? Any ideas?