I also have an '82 turbo. I was trying to track down a loss of power at high RPM and replaced my pre-pump. My main pump also became noisier. I went into the tank about six times changing pre-pumps from the original, to a used one, to the new one. The new one made the noise the worst. So I ended up installing a pre pump from a 740 turbo in there. More volume but a longer pump so the down tube had to be shortened a bit. End result was no more noisy main pump.

Much later, I discovered a plugged vacuum valve in the CPR tubing which was making my car run like crap until it warmed up.

I don't know if the pre pumps from turbos are different from Turbo, LH or regular CIS cars but the only thing I could find that would shut up my main pump was the bigger 740T pre-pump. IPD told me this was a factory service bulletin for a while.
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Volvo Farmer:

21 Volvos '58-'91

445-544-122-144-1800-240-740

sorry, no FWD

Just a wild guess... don't give it too much creedance. Perhaps it's the wrong pre-pump (ie. too much pressure), a bad regulator, or more likely a kinked fuel tank return hose. In short, way too much pressure on the fuel rail.

jorrell