Chip pack

[Guenther,Max]

I just got my 90 vette ecm in the mail and pulled out the chip.  Inside
the pack there is a home made looking monster on top of two smaller
chips(i dont know what the little chips are yet as I dont have the
courage to touch the monster)  Anyway what is it for?  Also does anyone
know the speed of the rom chip?  I found a 27c256- 150 is this ok.(i'd
leave the original alone)
Thanks, 
Max