Yes, the aftermarket chip is very worthwhile.
In order to gain maximum benefit from it though, you need to be able to have your car dyno tuned. That is, they make settings in the chip, dyno the car...make some adjustments in the chip, dyno the car... this process is continued until they have maximized what they can get out of your combo.
As for manufacturers, my recommendation is Johnson Motorsports in Lucedale MS.
www.jmschip.com. I have had nothing but good experiences with them, and Chris Johnson is one of the best in the business at tuning the Fox and Modular cars.
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1996 Lazer Red Cobra #878
ProM-80, 36# Inj, JMS Chip, Vortech-SQ, Pro 5.0 shifter, Bassani-X,
Borla Catback, 4.10s, FMS Alum Driveshaft