It is the same exact engine. Same internals, same externals, same ECU, same everything. If it runs great, then it runs great. The only thing that is different is the valve cover will say Infiniti. Easy fix. Go buy a used Nissan cover (2 are on eBay right now) and swap it out.
I buy ALL of my engine parts from the Nissan dealer for my Infiniti G20. ALL of them.
If you want to get technical,
The '91-'93 G20 and SE-R's are high port engine with no speed limiter and 7500 redline.
The '94-'96 G20 are low-port, has no speed limiter and a 7500 redline.
The '94 SE-R has no sped limiter, his low-port and a 7500 redline.
(This is where I loose it a bit)
The '95-'99 SR20 powered Nissan's are all low-port, have 6800 or 7000 redline and a speed limiter of 112 (???)
I buy ALL of my engine parts from the Nissan dealer for my Infiniti G20. ALL of them.
If you want to get technical,
The '91-'93 G20 and SE-R's are high port engine with no speed limiter and 7500 redline.
The '94-'96 G20 are low-port, has no speed limiter and a 7500 redline.
The '94 SE-R has no sped limiter, his low-port and a 7500 redline.
(This is where I loose it a bit)
The '95-'99 SR20 powered Nissan's are all low-port, have 6800 or 7000 redline and a speed limiter of 112 (???)