Slight lose of HP

[financialman]

Question for you guys. On my 94 I have noticed a HP loss at around 5800rpm to redline under full throttle. The CEL will come on as well for about 3 or 4 seconds and turn off.
It runs very strong up to that point and then feels "flat" until you hit the next gear. Only mods are a Chip from Marc and a cat back.

Any thoughts.