The Taimanov System

1.e4 c5 2Nf3 e6 3d4 pxp 4Nxp Nc6 5Nc3 a6 followed by Nge7 etc was what Taimanov himself gradually likely best. In recent times 6NxN b7xc6 trying to show a6 an anti-move has become very popular, so many play 5...Qc7 first to avoid this. With Qc7 , nge7 has tactical problems. Even in situations where nge7 is possible modern players tend to prefer other methods.

1.e4 c5 2Nf3 e6 3d4 pxp 4Nxp Nc6 5Nc3 a6 followed by Nge7 etc was what Taimanov himself gradually likely best. In recent times 6NxN b7xc6 trying to show a6 an anti-move has become very popular, so many play 5...Qc7 first to avoid this. With Qc7 , nge7 has tactical problems. Even in situations where nge7 is possible modern players tend to prefer other methods.
I find the wasted move caused by 5...a6 more than sufficient if they DO go for NxN, as they have pretty much given me a nice d5 stronghold... However, one must cover the e5 square very quickly or White plops a pawn there, and you have to settle for the ...b5 idea and develop your bishop that way.

After 6g3 Nge7 7Nb3 then Ng6 is particularly attractive square for knight. So quite a few games have gone 7...d6 8Bg2 Bd7 then Nc8-b6 etc maybe after b5. Quite elaborate manovers with this knight, and it is not clear that simply Nf6 is better, and finding other ways to deal with e5. Quite a few strong players have played ng-e7 with Nc8 but personally prefer more straightforward methods.
Taimanov has written a book based around ng-e7, and there are quite a few annotated games of his, plus other strong players, like Karpov, using this move.

Only a patzer would play 5Nc3 after 4...Nc6 why to block your own c pawn if black doesnt oblige you with 4..Nf6?

5.c4?! Nf6 6.Nc3 Bb4 and Black has a lot of pressure on the White centre. If you really want the Maroczy Bind, the line 5.Nb5 d6 6.c4 is a better way of playing it as now the Bishop can't come to b4.