It's a gasket. Replaced the throttle body on my grandparents Altima and replaced the old gasket with the Fel-Pro and like almost every other Fel-Pro gasket I've ever bought it works just fine. I think it may be a tad thinner than the original but it still works just fine. I think if you have an issue it's more likely to do with the mating surfaces than the gasket. Clean up the intake manifold with some fine sandpaper or steel wool and this gasket should work just fine. Lots of people skip that step and then blame the gasket. Also I should note that Altima, at least the 03s and 04s I've replaced the throttle body on don't like to do the idle relearn via scan tool. I've used a couple different expensive scan tools that have a throttle relearn option on them and neither has ever worked on 03 and 04 Altimas. Look up the throttle relearn procedure and do it manually. It's a pain and requires a lot of counting Mississippis and turning ignition on and off and mashing the gas pedal at specific times but it's still doable without needing to go to the dealer. I've done it probably close to a dozen times on different vehicles and I hardly ever get it right the first time but I always get it eventually. Once you get that done it should purr like a kitten.