Looking at the parts.cfg file for the engine precooler (
Kerbal Space Program\GameData\Squad\Parts\Aero\engineNacelle\engineBodyRadial.cfg), the part has three functions, which is
- a resource intake
- a container for intake air
- a container for liquid fuel
The whole part is mostly a copy&paste from the engine nacelle (
Kerbal Space Program\GameData\Squad\Parts\Aero\engineNacelle\engineNacelle.cfg). The only non-cosmetic differences are price and the lower "emissiveConstant" which is relevant to heat transfer between parts. So when the part gets really hot for some reason, nearby engines overheat a tad bit slower with the engine precooler than with the engine nacelle. That's everything. Nothing which directly alters the performance characteristics of attached jet engines.
tl;dr: no, it does not enhance performance besides providing intake air and fuel.