What can cause limp mode

[FFMan]

1994 Griff 500:So i'm cruising into work on a fine autumn day about 2000 rpm and it feels like the ecu went into limp mode.

Rough running and smell of unburnt fuel (I think that is what it was). No MILF light but then i don't think it's wired is it ?

I pulled into a layby, turned it off and then on (I work in IT :-) and it was fine for the rest of the journey.

The only change recently was i changed the ignition amp as i had had an occasional misfire. That seems to have gone to be replaced by limp mode.

I have Rovergauge so i can scan for a code later, but i wondered what can cause limp mode ?

[blitzracing]

Not sure of the exact list of missing inputs, but it can be as slight as an open circuit tune resistor. Loss of AFM input will make the car a pig to drive and stinky exhaust.