M16A swap - feels more powerfull but still sturgling on the highway

Hi guys,
Been reading here for a bit - now it's my time to ask the annoying questions:
My 2007vvt (automatic) started to overheat (probably a siezed thermostat) and also, it started to feel extremely weak.
So, to kill 3 birds in one stone - i decided to swap an m16a into it, sourced it from overseas (probably eastern eu/turkey), put it in, car runs fine, feels stronger down low (not by that much though). overheating problems disapeared as i also put a 72deg thermostat in it (barely passes 85C now)
thing is - on the highways, it still struggles to go over 110(kph).

i used the m16a injectors. and the car has a 2" lift by oldman, 215 bf km3 tires and a roof rack:
Currently i suspect a clogged exhaust of something of the sorts.
Any ideas?

 

The front or manifold CAT are known to disintegrate and block the main CAT, that would limit power at higher revs.

The other thing to check is the air intake and filter, again limited airflow will limit power at higher revs and finally fuel flow or pressure, but you should then see it running lean if it was fuel flow.

Robin

What colour is your transmission oil? The auto boxes are barely strong enough to handle the 1.3. I resisted putting a bigger engine in mine because I didn't want to cook it.
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How would you diagnose this? Get a manifold from a different car? "Sports Cat"? Just driving without the manifold would probably be useless since no back pressure is also not that good, right?

Regarding the color of the oil, i added a pretty big oil cooler, the temp of gearbox oil goes up to about 99C when i hammer it up the mountain to my house(10km of mountain road). I also replaced about 1 l of it.
Got a new strainer filter thing coming in the mail in a few weeks and a new tranny pan gasket, gonna replace both and put fresh oil in it.