You never hear of the Allies "Having Fits" wit hthem because they were almost always misidentified by the Americans as "strangely painted early model Fw190s".
It was the IAR-81Cs of Grupul 6 Vanatoare (6th Fighter Group) that virtually wiped out the P-38Js of the 71st Fighter Squadron over the ARR airfield at Popesti-Leordeni on Black Sunday (the ones lost over the Oil Fields themselves fell mainly to the Bf109Gs of Grupul 7 and Grupul 9, alongside elements of Jg53 and Jg77). Lt H. Hatch, who was credited with "5 Fw190s" was the only pilot to return safely. Initially the combined German-Romanian forces claimed the destruction of 43 Lightnings that day (51 all together, including claims by Flak gunners) for an actual loss of about 25 lighnings to all causes- while the USAAF claimed 33 confirmed kills, 6 probables and 8 damaged, plus 10 locomotives destroyed- against actual losses of 14 German and Romanian aircraft, including all non-combat types reported lost on that day. The 5 kills Hatch alone was credited with was optimistic, as a total of 3 pilots were killed and one badly wounded in the whole furball, and fewer than 10 total aircraft were lost in the whole melee- including several low-alt collisions.
And I think 2xMk151/20s and 4x7.9mm MGs is pretty good for a close-in dogfighter, which is why I say the 81c would be the best version to model. It was the fastest, best armed, and best armored of the series, and was also the only version to be equipped to carry DTs.