I have a 97 Wrangler with a 4 cylinder engine and a manual transmission. I have had it for about 6 months now and cannot figure out why it seems to lack power, and sometimes spits and sputters, and even backfires once in awhile. It seems to have difficulty when under a load. Takes quite a bit of time to get the vehicle to 65 mph. That's about all the speed I can get.
I have replaced the plugs, wires, cap and rotor. It has an aftermarket K&N air intake, and a riser on the fuel intake. I recently took it to a shop and they checked the fuel pressure and the exhaust. Both checked out fine. I don't have any check engine lights that come on.
I don't know what the problem might be..