Lift Pump Problems?

[Smokey1]

My 99 is having some problems when I start up. When I start up and shift into gear the engine "chugs" "chugs' "chugs" for about 10 seconds before it calms down. It has never happen in park, only in reverse and drive. It seems to happen more often If I start and quickly place into gear. I have been letting the engine idle for about thity seconds before I start to drive and this seem to help. Sig below