I in all honesty forgot about that type of stuff lol. Im a mechanic so most of that stuff I can and most likely will do myself. When I mentioned diy I ment stuff like I wanna make my own st200 style airbox and resonator delete. Infact I've already got a pretty good idea on the airbox and im pretty sure it'll work. I just wanna see the before and after numbers with a cob so it'll be closer to when I can afford the AP. One of the first things I wanna do is look at doing an intercooler sprayer. A good bit of what I wanna do won't be a huge increase in power it'll be more focused on cooling the charge.
Then you will probably not need an intercooler sprayer. Just a larger intercooler.\
If your not going for a lot more power say just a tune on a AP then the list is kinda of RMM, larger than stock intercooler, Aluminum radiator, suspension, maybe some braces that all depends on if you think they are needed. Some will swear up and down a tree that a 6 point is a must have while others will state all is needed is the front 2 point etc..
Exhaust is esthetic not needed but loved. Usually the minute you delete your sound symposer you will find you want to do something exhaust wise so as to actually hear your engine and not the inherent sewing machine tick that it does.
Crossover pipes are proven to show gains this was done by Jason at Dizzy Tune when he dyno tested intakes.
Last but definitely not least and bigger deal than a lot of people realize or even think of is putting in a LSD. I am strongly of the mind that it is a before hybrid or BT upgrade.
Why is because our cars are made to handle and the LSD should have come as a stock option as it helps considerably in the corners and making the car drive more stable over all. As well as making TQ steer pretty much non existent.
Its not cheap but since you are a mechanic I am sure you could remove your trans and do the install yourself thereby only spending around $800-$1100 on the purchase of one.
I hope this helps with a little more detail on what is needed for what you want to do.