Where are you seeing these inquiries? Is it a credit monitoring service or do you have hard copies of your reports?
Pre-approved offers show up on TrueCredit and other monitoring services, but your creditors don't see them and they don't affect your score.
"Hard" inquiries do affect your score, and should only show up when you have actually applied for credit.
I know for sure that TransUnion won't even consider a dispute over an inquiry, and I've heard the same about the other two CRA's. They say that an inquiry just shows that they provided your report to someone, and they know that they did, indeed, provide the report, so there is nothing to investigate.
TransUnion did suggest that if the inquiry I was disputing was obtained without permissible purpose, I should contact the person who pulled the report.