The La7 vis is poor, it's nothing like the P-51, not even in the ballpark. Sure, the P-51 is outstanding, but any number of other aircraft in the MA have better vis than the La7. It is one of the worst, though I don't think it is necessarily 'the' worst. It does hurt your SA though, especially to the rear.
The WEP in the La7 runs as long as the 190 and 109, a long time. The problem is with fuel consumption. With those planes you have drop tanks, and multiple fuel tanks to get you to the fight. In the La7 you don't, you are always burning the main tank. The main tank doesn't get very far on WEP. With the Typhoon if you want to go a fair distance you pack your wing drop tanks. Also, 1 hit to the main fuel of an La7 and you are a glider within 1 minute. A fuel hit in a P-51, Typhoon, 190 usually just means you become a sky-writer.. no real problem other than attracting attention. Hell, it might even help you and make you lighter in one of those other planes.
The La7 has a forward gun range, for what I would consider a 'makeable' shot of about D375. Anything more that that and your rounds are flying all over the place (un-real considering you'd think with them all cowl mounted you'd be better off). You also can't afford to spend the ammo on shots over that since you only have 150 rounds/gun. That's not a very large, or long, opportunity for an La7 to fire. Compare that to something like the P-51, or Typhoon for that matter. Effective .50 shot range (again, aiming and expecting hits) is probably D550-D600. I know I take those shots all the time, maybe not expecting crippling damage, but at least to put some rounds on target. That extra ~200 yards is HUGE. It gets worse on a tail shot, the longest La7 kill I've ever had was at D625, pure tail shot on someone who hit auto-level. I had to set it up and spent 350 rounds firing away to get the kill. I'd take a D625 tail shot in something with hispanos or .50s ANY time. that's money in the bank.. with hispanos you can probably expect to amputate wings at that range within 100 rounds fired (or less). With .50's I've made those same shots reliably out to D800... and would feel confident about landing rounds at that range. The La7 tail is weak too... 1-2 cannon hits in that area and it's gone, the wings seem fairly tough, and pilot kills are rare, but the tail comes off just as easy as other planes. How many of use have had D800 N1K's hammer out planes from the sky as we try and get away from them... that's the combination of the N1K acceleration and all that ammo... it's a true distance killer (as the C-Hog is).
The Tiffie and P38 are both bad matches for the La7... maybe the reason you are having problems. the Tiffie accelerates like a dumptruck, and the P38 is missing almost 40mph on the deck as compared to the La7. (I fly both a lot though cuz I like them too, they have style.... just look at my stats. I bet the La7, Typhoon, and P38 are my 3 favorite rides last tour).
I'm not saying the La7 isn't a great plane, it is, but it isn't some omnipotent plane in the MA. I fly it all the time, mixed in with a bunch of other rides, and every time I go to a plane that has .50's or hispanos my shooting % goes way up and I land kills I couldn't dream of in an La7. I think most of the La7 mystique is from the quick short range kills it gets (those D150 snapshots that rip both wings off), or getting caught low and slow on the deck and having little chance of running away regardless of your ride.
-Soda
