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More info if you want to identify parts. The upper intake on the 5.0 HO and non-HO differs as well. It's possible the HO intake was installed though as the lowers are the same but the upper is different.
Easiest way to tell is to remove the intake plate. Under the plate, you will see the HO cast into the manifold. If this is missing, it's not the HO intake.
Part number for an 1989 HO upper intake is RF_E8ZE-9425-E4A. The 1990 HO intake started with an F0ZE part number.
Other info on what should be on the car
Upper intake: RF-E8ZE-9425-E4A
EGR spacer: E7ZE-9H474-AC 62mm TB side/64mm manifold size
TB: E7SE-HB (stamped on lever) 60mm
That's what should be on your car. You can compare to see how it matches. If the sizes differ, or the part numbers differ, then it's a good sign there are more non-HO parts on your car. I beleive the upper intake manifold part number for a non-HO is RF-E6SE-9425-
Just to be clear on the implications of this. It does appear that in some point of your cars life, the original engine was removed, and the long-block of a non-HO engine was installed. The reasons for this are unknown, but someone did repin the ECU to make it work along with most of the correct parts needed to get it running well. Maybe it was done out of necessity (the only long block they could afford) or maybe it was done to flip the car as cheap as possible. If it was known, it should have been revealed to you. WIth the E6 heads and non-HO cam and possible other non-HO parts, your engine might be making 180-200HP rather than the 225HP it should be making. E6 heads also tend to fall out of steam at higher RPM. They typically offer good low end torque, so they feel peppy on the street.