Yes, they had to take some warhead out and add some propellant for the anti-G5 rocket. There's an answer for everything, but overall about the only Soviet equipment which has superior performance to western equipment is artillery.
I agree, artillery is the key:
- Prior to the war, Saddam make artillery an elite branch (like the French did in WWI). Talented officers and motivated soldeirs are assigned to it. Long range artillery is deployed into mobile positions in Kuwait city. The artillery is supplemented by brigades of elite infantry. They have supplies and plenty of decoys for a year.
-U.S. Marines advance to the outskirts of Kuwait City and get a nasty surprise. The Marines are hit by accurate and heavy mortar fire. Iraqi long range artillery and rockets hits units and convoys all overy Kuwait.
-Units bypassing Kuwait City quickly realize that most of the Iraqi army is is Iraq. There are no 73 Easterling Turkey shoots. As U.S. units near the Iraq border, they are hit by more lethal long range artillery fire from Iraq.
-There is no easy Coalition response. Grinding down the Iraqi artillery is going to take time and cost civilian casualties. Yet, Kuwait is not liberated when Iraqis still effectively contest large portions of the country via artillery.
Other annoyances: Iraqi Special Forces teams have ambushed several convoys inside Saudi Arabia causing heavy U.S. casualties and then melted back into civilian areas. Saudi police units trying to find these lethal teams are not exactly motivated or talented.
- A geo political military decision is made to storm Kuwait City. The city is taken, but hundreds of marines are killed in house to house fighting.