I have searched and found many issues similar but nothing quite the same as the problem I'm having. I'll post here to see if anyone can chime in if they have had the same problem and tell me what to check first. 1990 LX 5.0 5spd 106k miles Only mods are CAI and off-road H with flowmasters, and MSD distributor and streetfire wires. All mods done by previous owner I am getting quite a bit of hesitation or miss when the car is under load. It revs fine and drives fine with a constant, light throttle. But it seems like in any gear when you press the accel down, it will buck or hesitate or stumble. Noticed this morning that it actually drove good while still cold, then as soon as the temp starting to rise up, it started hesitating when a load was put on it. Once warm, it has NO issues starting back up. It also tends to idle a bit high at 1300 when coming to a stop, then it settles down to about 1000 or 950, still a bit high. Things I've tried: Adjusting the timing--It was set low when I bought it at about 8 degrees or so. I set it to about 13, saw hardly any change, except for when I first drove it when it was cold it ran great with no hesitation, then I took it on a trip and about 5 to 10 minutes in, the hesitation comes back. Set the timing back to about 10 and saw no change, possible a little more hesitation. Cylinder balance test came back clean with no codes. Normal scan came back with no codes. Any help would be appreciated, even if sending me to another thread I may have missed in a search. I want to isolate this problem and not just throw money away buying parts that are not broken.