If you're talking about the race start, it takes time/practice to start without loosing too much rpm (i.e., modulate the clutch to avoid spinning and keep rpm in the right zone). If you don't use clutch, try to use launch control button (dunno if the Metalmoro has one).
If on the other hand you're not talking about the race start, then the only thing I can think of is to check if you don't have pit limiter engaged by mistake or maybe try to reduce the AI strength a little.
Yeah, it's either a bug or it's just the way this car is made. I use autoclutch and the rpm drops heavily at the start, eventhough i have the throttle pedal pressed to max.
No other car behaves like this and i'm able to maintain high revs at the start and get off the line in a normal manner.
This has been updated in v1.27 but apparently not enough. The engine does not have a lot of torque in the low range so you would want to keep the revs up for a strong start, but it is indeed bogging down too much. It will be looked into for the next update.