vr6 problems from cold start

[mush]

I’ve been running my vr6 for around a 1000miles since i completed my project, however
Since having the de-cat fitted ive come across a few problems one of which is when i go
To start the car it runs very rough for a short period of time and total power loss after a few
Minutes of driving, i even had to pull over on a side road when i went for a drive yesterday as
It started spluttering and lost power. Sounds like its not firing on a cylinder.

Anyway revs were going up and down on idol then after about 2minutes of this happening it
Cleared its self and ran fine, after this i risked and completed a 40 mile journey and had
No issues with it after it was warm.

I need some help on this guys, anyone had the same issue? I don’t think its the de-cat
That ive had fitted i just think its developed this at the same time i had this done and its
Not linked to this problem.

Like i say its fine when warm, but on cold start up and it happening at junctions this
Is very concerning when pulling out and really need to get it sorted.

I’ve made a list on what i think it is but if anyone can help that would be awesome.

Spark plugs – (i haven’t changed them and they look old)
Air leak – ive checked and seems ok
Spark plug leads – they look ok
Crap fuel 95 ron – (would be like this all the time if issue with this)
coil pack

Help guys

[GOLF-MK3-GTI]

Scan it for fault codes first?

[mush]

i'm not able to scan it dude, i dont have the port to plug it in, its a mk2 vr6 forgot to mention that  . its a obd1 coil pack if that helps.

[Therusterman]

Maybe a coolant temperature sensor which is causing over fueling?

[GOLF-MK3-GTI]

Lambda sensor plugged in de-cat?

[benvictors]

Yep, coolant temp or lambda/oxygen or maf sensor
And 95 ron is more then ample for the VR engine, just use a branded fuel 

[tweed]

Broken wires or damaged lambda when changing it over?

[Deano2711]

If it is OBD1 then check and clean the Idle Control Valve......mine was very similar recently. Revs would drop when stopping and occasionally cut out. Then would sit and rev itself and always worse when cold. I removed the valve and cleaned as best I could. Re fitted it and it was poor for a short while while the valve re set itself but now its back to its best and purrs at 600 rpm when I stop no matter what.