Walbro in bucket soldering issues

Hi , my walbro install seemed to be rock solid , but that was only with max half tank filled.



Everytime I have filled gas , the car stumbles and act weird during startup , only after filling then acts normal again.



But lately I filled tank full and car wont start now , it cranks alot and when fire up only runs on few cylinders.



Im pretty sure this relates to my walbro install , cables from pump was soldered to connector and put shrinkwrap around.



I plan to remove shrinkwrap and replace with some form of petrolsafe sealant.



Anyone else had any similar experience ? Or advice on what sealant to use?



I tried to rev it , warm engine already , and after 1 min I gave up , also some smoke came from engine compartment so I dint want to destroy anything.



Reving was between 3000 and 4500 in attempt to see if it would wear off and run normal like it had done before.



Now car is in shop with fuel pump out of tank.