A revamped Diet Pepsi without aspartame is popping up on store shelves. So will people start flocking back to the soda? PepsiCo says its new Diet Pepsi should be available nationally this week. In response to customer feedback, the company said earlier this year that it would replace the aspartame in the drink with another artificial sweetener that has less baggage. The rollout will test the theory that the sweetener is to blame for fleeing customers, or if other issues might be at play. Other diet sodas that still have aspartame include Diet Coke, Diet Dr Pepper and Fanta Zero. Sales of traditional diet sodas have been falling. Industry executives blaming the freefall on unfounded concerns people have about aspartame. Two years ago, Coca-Cola even tested ads in select newspapers defending the safety of the sweetener."It's the No. 1 thing that our customers have been calling about," said Seth Kaufman, a senior vice president at PepsiCo. At least in the short term, Diet Pepsi sales are likely to see bump from the marketing push around the new formula, which will include in-store sampling and discounting in coming weeks. In terms of taste, Kaufman said it's not identical but that the drink should still be familiar to fans of Diet Pepsi. It's not the first attempt by PepsiCo Inc. to lift flagging sales of Diet Pepsi. In 2012, the company tried improving the drink by combining aspartame with acesulfame potassium, often called ace-K, another artificial sweetener that helps prevent the taste from degrading over time. The latest version of Diet Pepsi will also have ace-K in addition to sucralose, best known by the brand name Splenda. Cans and bottles of the new Diet Pepsi have been making their way through the distribution in recent weeks.