lmao thanks for all the man I appreciate it a lot. I plan on buying 1-2 more hellcat pumps and getting a new wastegate, I also believe the ffim exhaust manifold is leaking so would be good to go with a new one aswell. I want to use the haltech and haltech dash so I will need to iron out the harness issue. I am cool with getting bigger injectors aswell as the current ones lack...
Being 100% honest, I'd skip the Haltech dash unless your existing dash pieces are trashed. I've found that most aftermarket dash displays are either too bright at night, too dark during the day, or always in between and you're messing with the brightness all the time. Once you get the brightness dialed in I've found it's a lot easier to see needle angles in my peripherals than it is to read digital numbers on a display, so I just end up vastly preferring a primary gauge cluster that's all needle-and-dial for the primary stuff like the tach, speedo, temp, etc.
Something like a BTI gauge mounted in a non-permanent way over the clock or somewhere similar above the stereo so you can get the critical additional data like oil temps and peak boost and a/f's and all that.
Also, on the FFIM & exhaust manifold leaking, I'd do the proper testing for boost leaks and exhaust leaks before just throwing more parts at it. It really sucks to spend hundreds or thousands on other new parts to fix a problem, only to find out the problem was elsewhere and the expense wasn't necessary. So try to find ways to empirically prove you need something before getting the OMG-shiny-new-PARTS!!!! lust fired up - these cars will exceed any budget you set, so there's no sense making it worse if it can be avoided.
You will not need 3 hellcat pumps unless you're really going for 1300+whp on E85 or E98. Don't go overkill on any of that right now. If anything, buy the injectors you'll want in the endgame because that will save tons of tuning time and expense for your Haltech setup. Yes, you'll run out of fuel pump way before you run out of injector but it's a lot easier to add another pump/increase line size/etc and drive on, than it is to change injector size which means your tuner has to almost start all over again on the fueling side of your tune.
So cliffs notes
-Boost leak & vacuum leak test the hell out of everything
-Use an air compressor or even a bike pump to check wastegate spring pressure and proper operation. Replace the WG spring to one rated for ~14psi or so if it turns out you have a 7psi spring in it, which would explain why your boost controller was maxed out at 13psi. Replace the wastegate entirely if needed, again, 14-17psi or so is a good wastegate spring to start with.
-Verify your boost controller is installed correctly and working
-Acquire Haltech patch harness, work with your tuner to ensure it's installed correctly and set up for a base map.
-If it's within your budget, buy the 'never have to change them again' injectors. Given your 800-900whp goals I'd go ID1300X's or ID1700X's. The 1700's will give you more headroom on the injector side but idle quality, cruising mpg, etc will probably be slightly better with the ID1300's.
-Do that -6AN feed line as described to the stock rail. Install an adjustable pressure regulator with a gauge if you don't already have one. I really like the Radium stuff and recommend it.
-Double check your ignition setup and ensure you've got quality plugs with a nice boost-friendly narrow plug gap BEFORE your tuning appointment. I like NGK Iridiums for a setup like this, IIRC they're the BKR7EIX for the heat range 7 Iridium that fits the Supra but double check that, I'm on less than 4hrs of sleep in the past two days. Never buy spark plugs via amazon or ebay or any of that shit, tons of counterfeit NGK products are out there now. Buy only in person from an auto parts store. Bring an old spark plug to make sure the form factor and size is correct because the dude at the counter won't know.
-Fresh oil change and full tank of preferred fuel before the dyno day, do all the initial tuning on wastegate boost (should be within ~1psi of the rated spring pressure with the boost controller completely off) then let things cool down and start cranking up the boost. 18-19psi max on pump premium is a safe threshold for most setups like yours, and you should be a nudge over 500whp. On the corns, especially when the E% is above 70-80%, you can basically run it on 'full send' until you run out of fuel system. With the S366 turbo you have, you'll probably max that turbo out in the mid-high 700's to low-mid 800's (depending on cams, FFIM, exhaust size, intake temps, etc) and be making torque numbers right around the safe limit of the stock rods.
