So we have the Awesome. It's fast. We have the Atlas. It's slow, but it gets into close quarters combat plenty often. So why do we need the Mauler, a mostly ranged mech, to be as fast as an Atlas? Slower Mauler wouldn't be all that bad.
The Mauler gets shot through the side torso almost every time, so here is my solution: STANDARD ENGINE!
Now we could just pop in a Standard 190 and all the variants would be left intact as the Standard 190 weighs the same as the current XL 270. But the Standard 190 only goes 34 kph in a Mauler. Yeah, that's just a bit too slow. So I picked the Standard 230. It weighs 3 more tons than the XL 270 meaning I have to strip 3 tons off of every Mauler.
The Standard 230 goes 41 kph, by the way. (The XL 270 goes 49 kph)
2 LRM10, 2 ERLBL, 4 UAC2, 4 DHS, BAP, Eoptics
(Removed 2 LRM15, added 2 LRM10, added BAP)
1 ELRM15, 1 ELRM20, 2 LtGauss, 4 SBL, BHP, GECM, 2 HS, Eoptics, 4 Free Tons
(Removed 1 ELRM20, removed 4 Mgun, added 1 ELRM15, added 4 SBL, added GECM)
2 LRM20, 2 ERPPC, 4 LBX2, 3 DHS, Eoptics, 2 Free Tons
(Removed 4 AC2s, removed BAP, added 4 LBX2)
2 DSRM4, 2 UAC20, 4 SBL, GECM, 6 DHS, 2 Free Tons
(Removed Extra Ton of Armor, removed 2 Free Tons)
2 MRM40, 2 LPL, 4 SXPL, 7 DHS, 1 Extra Ton of Armor, 2 Free Tons
(Removed 2 ERPPC, removed Eoptics, removed 2 Extra Tons of Armor, added 2 LPL, added 1 DHS, added standard optics)
2 DSSRM6, 2 LBX20, 4 SBL, GECM, 0 HS, 2 Extra Tons of Armor, 2 Free Tons
(Removed 4 SPL, removed 2 Free Tons, added 4 SBL, added GECM)
2 Gauss, 2 LRM5, 4 ERMBL, 3 DHS, Eoptics, 4 Free Tons
(Removed 2 UAC10, removed 2 MRM20, removed 1 DHS, removed standard optics, added Eoptics, added 2 Gauss, added 2 LRM5, added 2 Free Tons)