My motorhome don't go past 30 mph and driving it I'll go2 blocks and it stalls

Hello, That sounds like a clogged catalytic converter. You can test this by connecting a vacuum gauge to one of the ports on the intake manifold and raising the engine speed to 2000rpm-2500rpm. It is very important that the engine speed stay constant. You then will watch the vacuum gauge to see if vacuum steadily decreases while at constant engine speed. If it decreases steadily, clogged exhaust. You may also have low fuel pressure, and this should be tested with a fuel pressure gauge.