502 500hp efi sumble /stall
 

engines are 95 502 mag 500 hp they are the efi models ( have the mechanical pump on water pump housing and the vst tank set up to provide a "head of fuel" to the electric pump that feeds the rail)
both engines run like a champ however the one engine(starboard) occasionally stumbles when getting on plane at about 2500-3000 rpm but it only does this given specific circumstances
1). boat has to have been run at least 30 min ( so is warm)
2). has to be shut off for an hour or two
if the above two situations have been met it will start and idle out of no wake but when goes to get up on plane at about 2500 to 3000 rpm the starboard engine will fall off to about 1000 rpm for a couple of seconds without moving the throttle will bounce right back up to 3000 and will be fine for the trip home

this is frustrating because this only happens if the above 2 conditions are met any thoughts would be appreciate
note engines have been recently freshened up

Likely vapor lock. VSTs on the big blocks are noted for doing this.

it does seem like a vapor lock , I thought the same thing but why only the starboard engine