X2. I have found all the early 1500s I have worked on to have weak accel pumps, even though they did not 'look' bad when removed.....An accelerator pump failure would compound the problem and be noticeable at your description of the symptom. Check for proper discharge of fuel from the pump nozzles at the top of the carb with air filter removed when twisting throttle....
Also, as Newday said, do a search and you will find info on the 88's carb. issues and how to solve them. I have one that is detailed on my 'fix', but not on how to R/R the carb.s as there are enough of those already.
No, checking the vac. lines is not hard once the carb.s are out.