Just picked up this fresh 1992 4th gen. Prelude!

THIS IS MY FIRST HONDA AND FIRST BOOSTED CAR! Im somewhat mechanically inclined just never owned a custom car w/ a turbo.
I PICKED IT UP ON CRAIGSLIST. THIS IS WHAT THE AD SAID:
"The car has probably 15-20 thousand invested into it so you will just have to come and see it to get all of the details. I will try to list as many things about it as I can.
Interior is leather with synth leather racing seats, racing red stitch steering wheel, Installed the electroluminescent cluster and harnesses from the 96 prelude.
Turbonetics T3/T4 hybrid turbo, 3" straightpipe exhaust so you get max power and can hear that turbo whistle, Greddy type S blowoff valve, Actual Tial Brand wastegate, Apexi electronic boost controller, JE forged pistons, Eagle H beam connecting rods, H&R dual valve springs and titanium retainers, Larger than stock stainless steel valves (so they flow more air and wont break at high rpm), Crower stage 2 Turbo cams, all manual timing belt components off of the H23 motor so at high rpm it has no chance of losing tension, ported head with a valve job 5kmiles ago, new pistons and rings 5k miles ago, new cranks and connecting rod bearings 5k miles ago, cometic racing head gasket, ARP head studs, complete rotating assembly including the clutch and flywheel are balanced even down to the bolt positioning for longer life and higher RPM, ACT Street strip disc with the ACT 400hp pressure plate so it works smooth and holds strong, AEM High flow fuel rail, Walbro high flow pump, Aem fuel pressure regulator, RC 750cc injectors Dyno tuned by Intec Racing in Kent, gets about 25mpg when you have the ability to drive it normally.
I am a mechanic and did all of the work myself. The transmission has new shift syncronizers so it shifts smooth, I put a KAAZ clutch type limited slip differential in the transmission so you get better traction and better cornering (since it is a clutch type it corners smoothly), Koni yellow adjustable struts, H&R Race Springs, Strut Bar, 5 Ziggen fireball rims that are pretty light and strong, jdm black housing one piece lights actually right off the Japanese prelude and matching black housing marker lights. This car rides smooth and doesn't bounce at all"
SO MY QUESTIONS ARE: (don't hate on me if i say something stupid, like i said im a newbie and just looking for some advice)
Need to rebuild or get a new waste gate (only opening up to 5psi at the moment)

what do u recommend?
The 3'' strait-pipes have a 2.5 inch exhaust slapped on the end.

(previous owner said id need a 3" one to match the strait pipe.) What are some good 3" exhaust?
I understand ill need to get the car tuned. It can push up to 14 psi safely. I want to be able to haul ass and still get good gas milage (somewhat). Do i have the ability to control boost w/o taking it in for a tune? dose the apex electronic boost control allow me to turn **** up or down? Id like to keep it low and save gas while just cruizin but then turn it up if i need to whoop on someone.
last question, my buddies talk this car down, i think its cuz they are jelly. I woop on there turbo'd civics even at 5psi. (barley but still). So it this car badd ass? and how much do you think i bought it for? just throw out a number on what you think its worth.
THANKS BALLERS