All fuel injected Rangers(1986 and up) have a stock Cold air intake, so you didn't install a cold air intake you just changed to a different cold air intake
No computer reset would be required
Did the MAF sensor get put back on?
The Ranger air filter and box had 200% of the air flow required by the engine, so filter could get pretty dirty before engine performance was effected
Are you using a smaller "cone" type filter?, if so remove it and see if power is restored, you can drive without a filter to test if that's the issue
And don't use "oil bath" filters, they foul up the MAF sensor
There is no real benefit in changing to a different cold air intake, except for looks, cause they can look way better than stock air plenums, lol
But they do need to preform at least as well as stock intakes or there would be problems
One tell tale of a problem, is sound, i.e. if you can now HEAR air being sucked in when you REV the engine, that means there is turbulence, so restricted air flow somewhere in the new system