I have a V5 Sti Type R with Simtek. After giving it full throttle on second gear the engine stalled and I couldn't start it directly but had to wait maybe 30s before it would start again. Took the car out from the winter break today but this happened to me once last year too.

Also the car can be hard to start sometimes when it's warm and needs to be cranked a lot longer than normal.

Could this be Simtek related (did not have this problem with stock ECU) or is it more likely to be a bad crank sensor or something like that?

AFR readings are fine.

 

my mates did that, turned out to be the maf.
but having simtec, it carnt be that.

the other one, is the crank sensor on its way out?
do you get any lights up, or get a diagnostic done

 

I would look more towards the fuel pump. Damaged wiring, faulty pump etc...

 

I can hear the pump priming so I don't think it can be it. Also the pump was changed last year.

No diagnostic lights, I don't think Simtek works that way other than lighting up the check engine light when it detects engine knock? I have the Simtek programmer kit but I'm not sure if it's possible to see anything odd there.