I understand that polystyrene standards will swell in THF, but not in toluene. So it is not possible to compare certain samples run in THF to the same samples run in toluene. Has any one seen this? Is there published works that may refer to this?

The standards will work equally well in both solvents

To clarify: I'm not so much talking about solubility, but the difference in hydrodynamic volume of polystyrene in each solvent

Yes. Who told you that they are different?

A column supplier and a chromatography test lab