I've taken the liberty of summarizing some quotes from Mike Kojima's link for your convenience, stating the gains that various mods will produce...
"You can safely run up to 15 degrees on premium gas on the GA16DEs. This has been proven by recent dyno testing on a stock car to give up to 5 more hp at the wheels in the midrange and 2-3 at top end. Remember if you have your timing turned up this high you MUST use 92 octane fuel. Do not exceed 10 degrees of advance if you have a JWT ECU."
"The Hotshot header gives about 6-7 more peak wheel hp than stock and 9-10 hp around 5500 rpm according to our dyno tests. This is pretty impressive for a header on such a small engine. A Civic is lucky to gain half of this."
"Most new cars only gain 2-3 hp from a cat back exhaust but not GA16 equipped Sentra! We found 6-7 hp to the wheels with our prototype Hotshot cat back system, an impressive gain."
"If your engine is naturally aspirated, limit your pipe diameter to no more than 2" or you will lose some bottom end with no applicable gain on top. For turbo applications, 2.5-3" is the way to go."
"Perhaps the most potent air intake is the CAI by Hotshot. I have tested this combo and found up to a 5 hp gain at 4500 rpm with 3 more peak hp."
"The JWT ECU adds an amazing 10 hp to the midrange of the power band and generally adds about 3hp on top. We found that the ECU gives the GA more power under the power curve than any single mod tried to date."
"After running the car, our SOTP estimate of power gain was moderate, about 2-4 hp. The engine felt more eager to rev and there was less drag when the AC compressor kicked on."
"On the dyno the pulley gave us 1 more peak hp but 3-4 through the often used midrange."
"the 95-99 cams have a bit more top end power, while the early cams have a bit more bottom end power. Overall if you are doing some junkyard raiding, the late model cams will give an early car a couple more hp"
"In my testing, the JWT did not lose bottom end power from stock (the bigger the cam generally, the less bottom end) and were good for a solid 7-peak hp. The gains were recorded from 5000 rpm on. At 7300 rpm the cams produced an amazing 42 more hp than the stock cams!"
"At this point the car is running 15.6@87 mph."
"the better head to use for performance work is from the 95-99 GA16DE"..."The new style head is good for about 5 more hp over the old style head."
"By going to 11:1 CR with pistons, a GA16 should gain 5-8 hp across the board. As I have stated before, a JWT ECU is mandatory with 11:1 to prevent engine-destroying detonation regardless of piston type."
"We tested the Extrude Hone process on our project GA16DE motor with excellent results. We experienced power gains from 4500 rpm on up with no loss of bottom end power. In fact we got big fat power gains from 4800 rpm on up, right in the zone where you shift at wide open throttle, so the whole useable powerband sees the increase. our gains averaged 3-4 hp in this range with a peak gain of 5 hp."
"After Extrude Honing our powerband is very broad and flat with over 110 hp available from 5400-7200 rpm! The motor rocks hard to the rev limiter! That's nice broad useable hp, not peaky narrow band Honda type hp. With the simple bolt on tricks we have been doing our project GA can hold a slight lead over a Civic Si even though the Si makes much more peak power. The GA16DE has less peak power but more area under the useable power curve."
"The GA16DE responds to this process better than the SR20DE does."
"On the Dyno, the larger throttle body did not help the peak power more than 1 hp but kept the power curve flat across the top for 400 rpm and gave 2 more hp past the peak from 6300 to 7300 rpm. Now the power curve is virtually flat from 6000 to 7300 rpm with no more than 4 hp deviation!"
"We suspect that once we improve the head flow, the throttle body will make a larger contribution to the peak power. However we also feel that on stock cars or near stock cars, the only difference will be an improvement in throttle response."
There is much more detail in the actual link and more information in the others links
There's nothing like a good drive to turn around a bad day.