Accelaration Hesatation

My Corolla which has stood for a good 1,5 years in total, I did use it here
and there during that time, but not every day maybe Once every Two
months or so.Has developed this Hesitation, only until 2700 RPM roughly
and then she seems to pull normal again.Its almost like a switch switching
off, or it changing over to a different fuel map or something..If you
accelarate slowly from pull off and then she is also fine, but the minute you
use say 30% throttle she starts to hesitate, but it almost feels like a miss.if
you hold her on say 1500 in first gear it actually sounds like its backfiring
into the intake manifold.The ECU does not report any fault codes or
anything.I have a Launch Diagun, Ive used that and ive done it manually by
counting the engine management light flicks.

Thanking you in advance for any advice.