ohhh icic. I hadn't quite seen the correlation between air filter & car behavior until just now lol..
anyhow, yeah I'm pretty certain it's just the difference between the ECU's and throttle mapping. Hence why people have reported that after an ECU tuning/upgrade, the throttle and power delivery is a lot smoother throughout the rev band, regardless of what gear you're in. Probably even in Reverse
jk haha