When you max out 60# injectors and have more than 2 alky nozzles, then you might want to look at options for more fuel delivery. Double pumper is one option, KB Boost a Pump and external pump are other choices to support bigger injectors.
FWIW, double pumper costs nearly 4 times what a Walbro 340 high PSI pump costs. There are other places to spend the $375 -$400 difference.
The alky kit just payed for itself as your not doing HG's and a fuel pump
Keep the tank full when racing, it adds weight over the rear tires, keeps the pump cooler, and eliminates any starvation issues.
Once thing is what the fuel pump can do when no load is on it, another is when it has to flow. If in doubt.. replace it. That is the best scenario. Doing tests with engine not running or idling proves nothing. Your fuel pressure gauge is the one telling the truth under boost/load.
+1 on adding gasoline.. and keeping the tank topped off.
If the sock on the fuel pump is clogged it will make 100 PSI pressure no problems but wont flow. Pressure does not equal flow. That is why doing tests when the motor is not under load leads to junk results.
In this case pump is fine, clogged sock is causing the issue. Open flow at no pressure proves nothing. Except it moves fuel.
If a 100 dollar pump is suspected bad, its cheaper in the grand scheme of time, troubleshooting, mental aggravation, etc to replace it. Especially on a car that its easy to do so. Once replaced you know its not the problem. Fat chance two are bad. And dont forget the filter.
Most shops charge 50-75 minimum labor to work on cars. Sir we have spent three hours diagnosing your car, and yes the pump is bad. 600.00
Fuel pumps going bad on Buicks is extremely common. That is why everyone always jumps to point that finger. Like bad stock/reman MAF's. This is a high failure item for these cars.
2 year old walbro pump suspected of problems.. end the drama and change it out