MrM3 is right the es started in '86, i have a grey one. the only real difference in the m-type steering wheel (can replace any non airbag steering wheel), and the front spoiler. as for the exhaust it is single exhaust the whole way. I would recommend checking the engine mounts i had to replace my '87 is at 160k and the '86 es at 170k, believe me it looks easy but unless you have a lift it is a pain. there are a couple places the oil can be coming from so be sure to check that a little more throughly as well, it could be a $40 part or more pending whats leaking, i've had problems with that too. also check to make sure the control arm bushings are good, they get kinda expensive if you try to go through a dealship, you have to replace the bushing, arm and ball joint to fix the problem. aslo make sure the timing belt has been changed every 60k, bad things can happen if it hasn't been.
those are the things i've come across in my 3 e30's, so take a close look.
the car sounds great though, i love mine and at 175k it runs great, and looks like it'll make 250k
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