Yes, mostly experience it when fuel up with shell 97. but i do experience it on mobil 1 fuel as well. it's on low rev when i wot there's slight knock on 3k rpm then the sudden surge at 4k rpm. and this usually happen on a hot sunny day. on a cool day eg 24-26'c car is smooth as silk. Suzuki Swift Sport with just some minor mods such as intake and exhaust with emu.