sounds like the infamous 3800rpm hesitation problem. Unfortunately i have no idea how to fix it but i remember reading about it somewhere on the net, try searching for 2nd gen faqs ont he internet, if i remember where i saw the document, i'll let you know
You need to add some more gounds. If I remember correctly, your ECU is not getting a good ground. You can run a new ground directly to the ECU, but I bet it would fix it if you just ran a couple 4 guage ground wires from the batter to the chassis and to the engine. I also grounded my exhaust at the y-pipe to my transmission. With a multimeter, I now have 0 resistance between any 2 points on my car.
I presume you have an NA. Check the thread further down "Dyno Chart" by Mallard Duck. That notch at 3800 is normal as the secondary ports open. If yours is worse the grounding mentioned earlier may be needed.
__________________ Bill ~ Black 91 Turbo ~ TOTALED 6/3/06
Recovering boostaholic now driving a 91 Miata.