Sportline bars are part of a factory option package so they will look stock.

Have a close look at the bar mount to body area. You might have a pulled spot weld causing the sheet metal to flex / oil can or there might even be a crack that flexes when loaded.

Also have a look at the front bumper to frame horn area for previous repairs.

Cracks / pulled spot welds on steel will often show a fine light brown rust from the metal fretting. Fretting is where metal rubs against metal causing it to slowly turn to powder. this fine powder rusts rapidly turning to fine brown rust.

You can also use this to identify two bolted parts that look tight but are really moving around.