Just towed a 15K lb trailer 300 miles with my new 390. First half was great, tons of power. Second half was alittle doggy. Found my vacume line going to my PCV valve fell off when I got home. Yep, burnt the crap out of the valves. I used stock replacement valves, hardened seats and bronze guides. I have to pull the heads and get them redone and wondering if I should do anything different. I'm definately going with quality stainless valves this time, but I'm wondering if I should change the sizes? I always thought the 2.02/1.55 valve sizing was alittle strange to me as I grew up with chevys and windsor fords with 2.02 or 1.94 intake and 1.60 exhaust. I built a 400 sbc with nice 1.94/1.60 heads and it was a very strong motor. Would it do any good to upgrade to 1.65" exhaust valves in my heads? Here's my engine-

390 +.060" plate bored, balanced, hypereutectic 9.5 pistons, 901 cam, performer intake, 600 edelbrock, D2te heads, headers dual 2 1/2 exhaust, DUI dizzy.

The motor cruises at 2200-2500 most of the time with occassional jaunt to 4500 or so. I love the low end grunt and if I would improve anything it would be the 2500 rpm + power without sacrificing grunt or mileage. I use a very good machine shop, but they're not sure if a bigger exhaust valve would make a difference as they've never tried it. Any suggestions? Anybody done this?