Cook and drain the pasta according to package directions for al dente. Rinse the pasta with cold water.
Make the dressing: Whisk together the mayonnaise, sour cream, chili powder, lime juice and salt in a large mixing bowl. Set aside.
Remove the seeds from the jalapeño pepper and finely dice it. Dice the scallions and chop the cilantro. Peel the avocado and cut it into bite-sized pieces.
Add the cooked pasta, corn, jalapeños, scallions, cilantro and avocado to the bowl of dressing. Gently fold together until combined. Sprinkle with crumbled cotija cheese.