Im not sure if you done the maf conversion or if it was done already when you bought the car,but make sure the map sensor doesnt have a vacuum hose attached to it,the port is left open to atmosphere on the sensor & the intake port/hose is capped.
If youve checked/replaced all of the vacuum hoses,there are plenty of other components that could be leaking vacuum too,not just the hoses.Solenoids,pcv valve grommet,gaskets (intake,throttle body,egr spacer,iac) air intake hose,injector bosses,etc.You can use propane,carb cleaner or water to spray suspect leak points,while the engines running.Youll hear an idle change when you hit a leak.
91 LX 342ci (10.5:1) - TFS 190cc (stage ll)
TFS Track Heat - Lunati 61011 (.549" .565")
Flowtech 1 5/8" - ProChamber w/ FM
QA1 Coilovers - KB Matrix System
Weld ProStar XP's