Receive up to $504 promo credit ($180 w/Welcome Unlimited, $360 w/ 5G Start, or $504 w/5G Do More, 5G Play More, 5G Get More or One Unlimited for iPhone plan (Welcome Unlimited and One Unlimited for iPhone plans can't be mixed w/other Unlimited plans; all lines on the account req'd on respective plans)) when you add a new smartphone line with your own 4G/5G smartphone on an eligible postpaid plan between 2/10/23 and 4/5/23. Promo credit applied over 36 months; promo credits end if eligibility requirements are no longer met.
$699.99 (128 GB only) device payment purchase or full retail purchase w/ new smartphone line on One Unlimited for iPhone (all lines on account req'd on plan), 5G Start, 5G Do More, 5G Play More or 5G Get More plan req'd. Less $699.99 promo credit applied over 36 mos.; promo credit ends if eligibility req’s are no longer met; 0% APR.
There should be no need to optimize the Mac. The TCP/IP stack on OS X (ultimately BSD/FreeBSD-based) is robust enough to handle most modern connections without issue, especially anything on DSL. FiOS is another story however...
But in case you still wish to run it, use this if you have FiOS: http://support.apple.com/downloads/Broadband_Tuner_1_0
I would not bother on DSL though.