12J fuel lift pump spacer

Is the spacer necessary with the fuel lift pump? I ask because i changed my fuel filter, bled out the system and thought all was well. Drove it to work and the Landy stalled. Had it towed to a garage and they replaced the lift pump as I did not have time. The landy is still stalling out. Don’t now if fuel starvation...as it the motor warms up, the revs get high and the motor sputters and stalls. I notice that there was no spacer.