Another possible power loss and erratic idle cause

[Prof]

In getting the car ready for the MOT today, I noticed that the single belt I have on the alternator was looking a bit poorly so I swapped it out for the 2nd belt (it\'s supposed to be a dual pulley, but the old one was all worn and was killing belts, so I was running with a single pulley until my other one arrives).
 
Anyways, I thought I\'d done it up good and tight with a tiny bit of waggle in the belt, but clearly not enough - car started ok this morning, but as soon as I went to put my foot down - it was backfiring, stuttering, losing power and generally being quite erratic.  Came off the throttle completely and it settled down.  Anyways - limped into a housing estate and tightened up the belt a little more - also slackened off the power steering belt as that was a bit tight - pressed the gas pedal - bingo - working fine again. :driving
 
I\'m not quite sure whether this was just the belt slipping a little on the alternator and resulting in electical power loss or low voltage, but it really made the car quite sick - and such an easy thing to check for and fix.  If you\'re going to tighten the alternator without help - you need to take something to leverage the alternator off the engine, whilst tightening the adjuster bolt with the other hand - thank god for ratchet spanners !