As you can see in this picture that is always used regarding this battle, there's a strange unit besides de III./Pz.Gren it seems it is called JG. 9, always felt strange to me, like what does it means? an air unit maybe a contraction of Jagdgeschwader? why there with the infantry so close to the front? maybe it was meant to mean an antitank unit? I then looked around, felt that the "I" near the top-right where it says 46. Inf. Div looked oddly similar to the letter "J" in JG. 9 and realized it probably means not JG.9 but IG.9 !

And regarding this material on an old page about rumanian army in ww2, we can see the structure of the Divizia 1 Garda.

I'm posting pictures because the page behaves strangely and tries to redirect you to another ad page, but if you want to try, go to http[:]//www[.]geocities[.]ws/dangrecu/D1G.html, remove brackets.
As you can see, it says it is composed of three regiments, Regiment 6 Dorobanţi de Gardă "Mihai Viteazu", Regiment 2 Vânători Gardă and Regiment 9 Vânători Gardă.
in the same page we encounter the next piece of evidence on the composition of this Rumanian unit, that 'fell back' in disarray leaving the Grenadier regiment in a predicament.
26.4.44: the Tactical group 'General Opriş' was established (assigned to the German GD Panzer Division); during the following days this group stopped all the Soviet attacks.
good, it participated in First Targul Frumos too and gave good account of itself.
but then...
2.5.44: finally, the Soviets broken the Group's defence lines; it withdrew to Dumbrăviţa / IS and Ruginoasa / IS (W of TÂRGU FRUMOS), then S of the fortified line maintained by the other Romanian units.
And finally, on the book "Tigers of the death's head" is this paragraph mentioning the unit.
On 12 May, SS-Sturmgeschütze-Abteilung 3 deployed a single company under SS-Obersturmbannführer
Muller toward Oboroceni. On the twenty-sixth, it relieved elements
of Sturmgeschütze-Brigade 228 assigned to the Romanian Brigade Opris. Another StuG
company with eight StuG’s was deployed on 23 June and attached to the Romanian
Guards Brigade and returned to divisional control on 1 July.
So, in my opinion the 'General Opris' Brigade was the Regiment 9 Vânători Gardă (Infanterie Garda 9 or maybe Infanterie Gruppe 9 in the map) with maybe a battery or two from the StuG.Brig. 228 attached and according to the first map here in the beginning and in the page I mentioned about Romanian army history, it was in fact assigned to the Pz.Gren.Rgt "GD" in contrary to what Manteuffel said in the now famous report about this battle that he did not mixed his forces with Rumanians. Of course, this is all conjecture as I do not have access to first hand documents. Maybe we learn later other units assigned to this Romanian Brigade.
Bonus Stefan Opris picture.

Other mysteries to me is where was the II./Füsilier located and why are there two III./Grenadier units on the map above? maybe the top one near point 197 is the II./Füs ?
Thanks.