The cassette with the EQ. I believe the pushbutton volume/balance controls had gone away by then. Of course, the subwoofer and amplifier. The cassette with EQ was a fairly common unit in other Pontiacs. (Other GM cars too, but they didn't have the red backlighting.)
Within a year or two a CD headunit became available that looked just like the factory cassette. They're fairly uncommon, though.
[This message has been edited by Raydar (edited 05-09-2012).]
The above Delco Pontiac CD head unit is the one that most closely matches the factory cassette/EQ radio that came with most performance sound systems in 87/88. I have this unit in my 88. It plugs into the factory perfomance sound wiring using a factory GM harness and antenna adapter kit. These units were only available in early top end Bonneville's, Grand Prix's and Firebirds. I believe the last year this style was available was 1994. Thre are not many of these early CD's out there, but they look like they could have been installed in the Fiero from the factory.
I have run this system in my Fiero for years and it has been trouble free. Later Delco units tend to develop problems with the volume control. You should check this before you purchase one of the newer versions.
Delco also offered a similar EQ Casette in the Fiero that was all push button instead of having the volume and tuning knobs. They are not as easy to adjust while driving but were an available option on the Fiero with Performance Sound.
Will any of the Delco CD units mentioned here play MP3 or WMA files burned onto data CDs (which will provide several hours of music), or are they all limited to playing "proper" audio CDs (which basically use large WAV files)?
The description on that one says it has a tuneable equalizer. Guess they went that route because there wasn't enough room for a slide button equalizer. My Ford radio is designed that way. I don't know about the performance sound compatability. Someone else will need to answer that, but if the premium sound gets its input off the standard Fiero harness, then by using the plug and play adapter, it should function.