The limiting factors could be either the crappy stock wiring (quite a few ppl have reported about changing out the wiring completely with higher gauge copper wires) OR the stock battery capacity being just enough to handle the FI and electronics on the bike. It does not hurt to just replace the FI pump wire with a higher gauge one and check if that helps.
You can also ensure that the battery is fully charged up and then see if the pump still stumbles when the rad fan kicks in. By this you can eliminate these causes and narrow down the issue.
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