***HEADER/Exhaust***
Biggest issue with the exhaust is finding the down pipe. there are several ways around this. most 20V come with the stock exhaust manifold "header" attached but the down pipe is either removed or cut. if it's cut, you could have the a flange welded onto it to attach to your exhaust system. one of my friends(ceTna) found a $160 shipped full stainless cat back system for 93-97 corolla on ebay. now if you got that, then all you would need to do is attach the header to it. there lies the problem. between finding an original down pipe and a header, they seem to both be like finding a needle in a haystack.
SCT passed me some info from a friend of his. he pointed me to sv3Power.com and they have a downpipe for MR2 running a 20V. if you get the "racing" pipe, it will bolt up to the stock header and then you will still need to put a flange on it. it comes "some assembly required" but you can get it with either a flange o2 sensor or a threaded bung. that's a whole different problem... and i will cover that in a bit. an alternate i've found is to use a ae92 GTS 16V header. the exhaust ports line up, but you will need to grind/shape the flange to allow the end 2 bolts to work. i purchased an OBX one and it fits.
but there are some mods that need to be done. in the next few pictures you can see how the holes line up and how much they need to be modded to fit.
you can see the markings needed to be ground to get it to fit. i used a carbide bit on my die grinder and it was about 10 minutes of grinding.
i'll post pictures of it installed tonight once i get the washers to bolt it in. but don't forget to check where the stock EGR port is welded in. they really didn't clean up the metal before the welded it in and it would impede the flow.
now to plug that hole, you will need a M18x1.50 bolt. i might have found one(oem toyota part) that can be sourced from a junkyard, or from toyota for $2. again it's on order and once it get's in i'll post how it sits.
and being that the header is stainless steel, once you install it, before you fire the motor, wipe it down with rubbing alcohol on a clean rag. that way your finger prints won't become permanently etched into the metal. you'll get a nice blued finish instead.
back to the o2 sensor. i was able to use a 93 MR2 Turbo one, but i had to repin it. upon changing things in my new car, i found the stock 95-97 corolla secondary O2 sensor has the correct plug, but wrong flange for the header O2 port. if you get the Sv3 "racing" pipe,you can get the threaded bung and it may allow the 95-97 O2 sensor to work. i will confirm once i get the car running if it's something that will work or not.
******EDIT******
ok so i ground down the areas that needed to be ground.
and got the header to fit
it does clear the oil filter, but down below there's other problems.....
it hits the oil pan. and the O2 sensor hits the sway bar.
to fix these this is what i did.
tried a 1.8L down pipe off my old header, that was too long and didn't clear the cross member. a 1.6L might, or shortening this one would have, but i didn't want to do that.
wound up using header wrap. and seeing if i could bend it a little away from the oil pan. got enough clearance.
o2 sensor fix.
using the 95-97 stock downstream o2. hope it works without a CEL.