Testing Website Speed – How to be able to do this acuratly?

Hi there
So Im using your plugin specificaly because i have some issues with speed of our website thats most probably due to plugin conflictts. But now i have seen that the momentt i run the staged site`s url through page speed insights then Page speed insights pics up he login page – and gives me a 100 score on nearly everyhing. how can i get around this as i need o switch all [lugins off and back on one by one o find the problem

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