buy maf cleaner spray at your local autoparts store and clean your maf. Also, reset your ecu. These are cheap/free solutions that may or may not fix your problem, but the ecu learns as it goes, sometimes altering performance. A dirty MAF can also cause hesitation. Be careful when you clean it, and be sure to watch some videos on youtube; there's a bunch. By the way, congrats on staying on the na path with future plans for the cams and 80mm throttle and all that. For some time i lost my faith in NA 2j'z but i learned more about how to mod them, and they're really great engines. The is300 has a certain feel to it that not every car has and the engine is the heart of the car and plays a big role in that. It has character. A 5 speed running that time in miami's fall-transition weather with the mods you have seems low. I'm inclined to think the root of your problems is the hesitation and launch. Once in a stock auto with an open diff, I managed a 1.4 60 foot because of the lack of power. After the launch, it was slow af. Maybe it wasn't recorded well, but a second lower 60 foot= 2 seconds lower in the 1/4 and that has been tested. That means your car is abnormally slow off the line and makes up for it with a strong run afterwards. 15.4 is what id expect stock open diff auto car with 150000 miles to run in hot weather. You have coils which have stiffer springs than factory. That increases load transfer to the tires which causes loss of grip. This can make you hook worse, increasing your time. I suggest you make them full soft in the rear if they're adjustable when you drag race. The open diff can make times longer too. If you fix the hesitation, add an lsd, and soften your suspension, you 60ft should be noticeably lower and so will your quarter time. Considering you want the 4.3 diff, your car will launch and accelerate much faster. You'll encounter a traction issue until you upgrade your tires (from a 225 to 255 is huge and u can launch at a higher rpm) with the shorter ratio, but the car will make up for it in the rest of the run because the car will accelerate much harder. It's an excellent mod. Good luck. By the way for your ignition system if you haven't finished replacing it yet, I'd suggest ngk iridium ix plugs, ngk wires, and check out napol performance replacement coil packs. Supposedly better than typical aftermarket coil replacements and they're cheaper ($150 for a set vs $60-80 each for regular aftermarket replacemnts) you can find them on amazon. The plugs come pre-gapped, but check the gap anyways, and have fun taking the intake mani off. GOOD LUCK!