My understanding is that this is not a sound attack. With best play white loses because he sacrificed a whole piece. But in amateur play it is a strong attack and is fun to play. A similar line is the Allgaier Gambit a variation in the King's Gambit, also not sound but fun to play. You Tube has some nice vids on both.
Fried liver attack.
Thanks that helped a bit. It seems I'm better off somewhat avoiding the mess via 5)... Na5 leading to interesting game
My understanding is that this is not a sound attack. With best play white loses because he sacrificed a whole piece. But in amateur play it is a strong attack and is fun to play. A similar line is the Allgaier Gambit a variation in the King's Gambit, also not sound but fun to play. You Tube has some nice vids on both.
While the Allgaier is likely unsound, in theory if not also in actual play, I'm not sure the Fegatello is considered as such. I haven't researched it, but a quick look into databases shows White winning the great majority of games after 6. Nxf7.
for example:
Chesslab online, in just games from 1991-present, shows White winning 77% vs. Black's 18%, in games prior to 1991, White is shown with a 90% win rate compared to Black's 9%.
365chess gives White with 73% vs. Black's 18.4%
Chess.com only gives 8 master games with White winning 87.5% against Black's 12.5%
Chessgames.com give White's overall win results as 84.6%
That doesn't sound like an unsound opening's stats.
I think the Knight sac isn't so much a true sacrifice as it might be a deferred exchange since White's attack can be overwhelming unless Black is willing to give back material to break it. I do know, as much as I like defending, I'd much, much, rather be on the White side of the Fried Liver.
"It seems I'm better off somewhat avoiding the mess via 5)... Na5 leading to interesting game"
You may want to investigate 4. ... Bc5 if you like interesting.
I was playing a game and my opponent played an opening I had not seen before upon looking it up I found out it was called the fried liver attack the game was quickly decided by my opponent blundering his queen but I was curious what the main ideas are for each side in this opening.