Direct proof of use
The 2A28 Grom appears in the 1990 Gulf War through Iraqi BMP-1 infantry fighting vehicles. Weaponsystems.net identifies the BMP-1's main armament as the 73 mm 2A28 Grom low-pressure cannon, while the U.S. Army describes a BMP-1 displayed at Rock Island Arsenal as an Iraqi Army vehicle that served in the Gulf War and was found abandoned west of Kuwait City in 1991.
A separate Tank-AFV.com account of BMP-1 combat history states that Iraq had about 1,500 BMP-family vehicles in inventory by 1990 and describes Iraqi BMP-1s in Kuwait and Republican Guard service. In its Battle of 73 Easting summary, it records an Iraqi BMP-1 knocking out a U.S. Bradley with its 73 mm gun, with the second hit penetrating below the TOW launcher.
Sources: BMP-1 | Weaponsystems.net, RIA Self-Guided Tour: BMP-1 Armored Personnel Carrier, Tank-AFV BMP-1
Timeline
By 1990, Iraq had BMP-family infantry fighting vehicles in service, including BMP-1s and variants or copies described in public vehicle histories. Those vehicles carried the 73 mm gun as part of the BMP-1 weapons fit.
During Operation Desert Storm in 1991, at least one Iraqi Army BMP-1 was abandoned west of Kuwait City and recovered by U.S. forces. On 26 February 1991, Tank-AFV.com places Iraqi BMP-1s in the Battle of 73 Easting and attributes a U.S. Bradley loss to 73 mm fire from an Iraqi BMP-1.
Sources: BMP-1 | Weaponsystems.net, RIA Self-Guided Tour: BMP-1 Armored Personnel Carrier, Tank-AFV BMP-1
Operational role
In Gulf War service, the 2A28 was not fielded as a separate artillery piece. It was the BMP-1's turret gun, giving Iraqi mechanized infantry vehicles a short-range direct-fire and anti-armor weapon alongside the vehicle's coaxial machine gun and missile rail.
The strongest documented use is Iraqi employment. The U.S. Army source supports Iraqi BMP-1 service in the Gulf War, Weaponsystems.net supports the carrier-to-gun relationship, and Tank-AFV.com supplies the specific 73 Easting account of Iraqi BMP-1 73 mm gunfire against a Bradley.
Sources: BMP-1 | Weaponsystems.net, RIA Self-Guided Tour: BMP-1 Armored Personnel Carrier, Tank-AFV BMP-1