Your cold air intake may give a placebo boost in performance but it won't in reality. Not to mention its air filter is totally ineffective at filtering out the fine dust and dirt that is so harmful to engines.
The factory air intake is absolutely the best air intake to use, and it was designed to easily flow far more air than the engine could consume at wide-open throttle and redline rpms. Unlike many other air intake systems, the TJ's is not (!!) restrictive in the least. It was purposely designed to be non-restrictive.
A throttle body spacer will not help even .001% either. Nothing, nada, zero. Spacers can and do help performance when placed under "wet" air intakes like carburetors and the old first-generation throttle bodies that had a fuel injector in them. The TJ's throttle body is a second-generation "dry" type in that only air passes through it and the intake manifold. Fuel is injected below the air intake so no fuel passes through the throttle body. Installing a spacer under newer generation "dry" throttle bodies like our TJs have does absolutely nothing except cost you $$$ and make the manufacturer $$$. Really, don't waste your $$$ on a spacer.
4-hole injectors are controversial. At best they can smooth out the idle but they won't actually improve performance over the factory fuel injectors. The reason is that 4-hole injectors don't put more fuel into the engine than the factory injectors do. The engine computer won't allow that since it very tightly controls the air/fuel ratio. Once the computer, via the O2 sensors, is told there's enough fuel in the air/fuel mixture, it cuts the injector off so it won't spray any more fuel. So once either type injector has sprayed the correct amount of fuel, the computer cuts it off. 4 more holes in the injector won't change the performance or HP at all.
How can you improve actual performance? If you're running bigger than stock tires, that has a dramatic effect on performance. Bigger tires are harder for the engine to turn, plus at 65 mph (for example), the engine rpms are lower for big tires than they are for smaller tires. Lower rpms with bigger tires means less power. The engine actually puts out more power at the same speed than it would with bigger tires that reduces the engine rpms.
If you're running bigger than factory size tires, you can regear your axles to a lower ratio that will raise the engine rpms enough to restore the power lost by having installed larger tires. Doing that is common but it's not cheap to do.... costs average $1200-1600 to regear both axles. I personally have regeared both of my axles three times due to bigger tire sizes on two different Jeeps. Regearing a Jeep can produce a DRAMATIC boost in power.
I known when I was 19 I was all about more power but it took more than a few years to finally learn what helps and what doesn't. Avoid things like different air filters, "performance" spark plugs, throttle body spacers, etc. and use that $$$ elsewhere where it can really help.
I hope this helps. Understand the above does come from personal experience.
