So despite some work, and the car running better, I'm still having some issues w/my 305 TBI car at times.

Most of the time, it seems to be running fine. At times though, it has trouble starting, perhaps a bit more than it should? I accidentally stalled it in reverse yesterday, and it took me several tries to get it up and running again, a couple of times which resulted in the engine firing up, but then dying. When I finally got it going though (through more gas pumping), it didn't seem too troublesome.

Occasionally, it will idle slightly rough at times, but smoother most of the other time. Also, while I don't go crazy w/it, if I do step on it, the check engine light likes to come on . I do have a bad EGR valve though, so I'm guessing that might be the cause of it?

Hoping it's not a fuel pump, and something some injector/carb cleaner might help, but what do you guys think?

P.S: Gas-wise, I seem to be getting ~15 mpg mixed. Is that normal for a 5-speed 305, cause other people seem to do a bit better than that (not that I bought this car for fuel economy, just curious!)

 

could be a fuel issue indeed, i'd check fuel pressure in idle and under load. might want to replace your filter before calling out a dead pump.
btw my TBI (700R4 and 3.27 rear gearing though) is on a bad (chip) tune right now but i got 15mpg on my last ride, that was one third autobahn at around 90-100mph, one third spirited driving through the hills and another third of city driving. so either you're shifting that manual real bad, driving like an a$$hole (as in way fast all the time), or something else is way off

 

I had a bad injector once. Changed it and everything magically got better. New fuel pump also helps. How many miles on the current one? And of course the cheapest fix is the fuel filter.

 

Well, I'm not sure at all when the injectors were last changed. It is a project car I picked up dirt cheap after all, and it badly needed an oil change and air filter just for starters, which I got to this weekend. Basically, it's running better than it was, but still needs some attention.

I'm pretty fluent in driving a standard, and the only time I really drive like an @$$ is on the freeway entrance ramps. I mean, come on! Long, clear straightaway = too tempted to gun it . And that's the only time the SES light kicks in, and it's almost as if it starts really lacking top end power (like it's not getting enough gas).

I think I'm going to try these possible solutions in this order...

Run injector cleaner through a tank of gas?
Check the fuel filter?
Check the injectors?
Check the fuel pump?

Would that be the way to go about it?

P.S: With normal driving, what kind of mpg should I be expecting out of a 305 TBI 5 speed anyway?

 

Don't know how long that thing has been sitting. If more than a year i'd probably first drain the tank by unplugging the filter, change filter (just cheap insurance and avoids one variable) and refill the tank. Then go ahead and pull trouble codes if you get the SES light - this is very important for any further troubleshooting!! Some injector cleaner or seafoam would also help i'd guess, but i'd do the procedure i mentioned first nevertheless. After taking some care of the fuel system go ahead and test fuel pressure.

I'm not sure on your milage but since i drove my Formula around 19 mpg with the A4 when it was still all stock I'd venture to say it should be somewhere around 25 with an M5 and your lower highway speeds, of course depending on where and how (but doesn't sound like that'd be an issue) you're driving.