Help needed please

have recently bought a new chip with ALS
I have now got round to to test it, and something seems a bit strange.

If I activate it via a switch, when the engine is cold, it will drop the rpm, and car becomes undrivable. Now I know that it is not supposed to pop and bang when cold, but seems wrong that it affects the way the car drives. I was of the impression that it just wouldn't activate if some of the ALS parameters wasn't met (like engine cold).
Have I misunderstood this - or installed it incorrectly?

When engine warm and if I rev it, it will pop a bit - but I will not test too much if something is wrong.

I have connected PIN 13 through an on/off switch to chassis earth.
And modified the ISCV - but no other modifications. (descriped as very mild ALS in the instructions)

any inputs highly appriciated

/Heitmann