I dont knwo about your vacuum diagram but I'm pretty sure the HO stands for HIGH OUTPUT... Its basilcay what they slapped on the MUSTANG engines... they used the 5.0 in other cars but the mustangs got the HO badge and some mild performance add ons
-as
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'89 GT Convertible:
TFS TW Heads, TFS Street Intake, TFS Stage 1 Cam, FMS 1.6 RRs, 24# Injectors, Pro-M 75mm MAF, No Name CAI, 3.73s, O/R H-Pipe, FlowMasters, AOD w/ Trans-Go Shift Kit
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