I can see you're having trouble separating that which is required of a Congressman, and that which is not. I can petition, that is request, that he put my special interest before the commitee that is deciding on a funding bill, he has virtually no choice but to do so. You can argue all you want to the contrary, but the simple fact is that Congressmen don't have 100% choice in what they do. Also, my Congressman is my representative to every government agency by law. If I'm having difficulty with a non-responsive agency, my Congressman must, again by law, find out what the problem is. If you've got federally funded highways within your district, or need a new federal highway (see post roads in the Constitution), then requesting those funds isn't unConstitutional.
I see that there are those with their collective knickers in a knot over the Shrimp industry. That's a federally regulated industry, and since that's the case, they're limited by the federal government extensively. In exchange for that, and the fees and taxes they pay on their catch, they ask for and receive federal funding to enhance their regulated business. Really, I shouldn't have to lead you folks by the hand through this, aren't we all adults here?
Those are Constitutional requirements, and no, they're not in the Commerce Clause. The House of Representatives sets the rules under which all Congressmen must function. When you're elected you must live with those, or attempt to convince the others to vote to change the rules.
Now, do a little research and find out for yourself.